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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Jun. 30, 2020	Aug. 04, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Trading Symbol	CBT
Entity Registrant Name	Cabot Corporation
Entity Central Index Key	0000016040
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		56,461,543
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	1-5667
Entity Tax Identification Number	04-2271897
Entity Address, Address Line One	Two Seaport Lane
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02210-2019
City Area Code	617
Local Phone Number	345-0100
Security Exchange Name	NYSE
Title of 12(b) Security	Common Stock, $1 par value per share
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes

Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales and other operating revenues	$ 518	$ 845	$ 1,955	$ 2,510
Cost of sales	449	675	1,592	1,996
Gross profit	69	170	363	514
Selling and administrative expenses	52	65	230	208
Research and technical expenses	13	16	41	47
Specialty Fluids loss on sale and asset impairment		8	1	28
Income (loss) from operations	4	81	91	231
Interest and dividend income	1	2	7	6
Interest expense	(13)	(14)	(41)	(43)
Other income (expense)	(3)		(6)	(6)
Income (loss) before income taxes and equity in earnings of affiliated companies	(11)	69	51	188
(Provision) benefit for income taxes	5	(30)	(9)	(43)
Equity in earnings of affiliated companies, net of tax	1	1	2	1
Net income (loss)	(5)	40	44	146
Net income (loss) attributable to noncontrolling interests, net of tax	1	8	10	22
Net income (loss) attributable to Cabot Corporation	$ (6)	$ 32	$ 34	$ 124
Weighted-average common shares outstanding:
Basic	56.5	58.2	56.7	59.1
Diluted	56.5	58.4	56.7	59.2
Earnings (loss) per common share:
Basic	$ (0.12)	$ 0.55	$ 0.59	$ 2.08
Diluted	$ (0.12)	$ 0.55	$ 0.59	$ 2.08

Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (5)	$ 40	$ 44	$ 146
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	31	1	(4)	(15)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax	(1)	(1)	(3)	(3)
(Gains) losses excluded from effectiveness testing and amortized to interest expense, net of tax		1	1	1
Pension and other postretirement benefit liability adjustments, net of tax	(1)	(1)	(2)	(23)
Other comprehensive income (loss)	31	2	(4)	6
Comprehensive income (loss)	26	42	40	152
Net income (loss) attributable to noncontrolling interests, net of tax	1	8	10	22
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	2	(2)	2
Comprehensive income (loss) attributable to noncontrolling interests, net of tax	3	6	12	22
Comprehensive income (loss) attributable to Cabot Corporation	$ 23	$ 36	$ 28	$ 130

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Current assets:
Cash and cash equivalents	$ 162	$ 169
Accounts and notes receivable, net of reserve for doubtful accounts of $2 and $3	362	530
Inventories:
Raw materials	88	107
Finished goods	250	305
Other	55	54
Total inventories	393	466
Prepaid expenses and other current assets	66	45
Total current assets	983	1,210
Property, plant and equipment, net	1,412	1,348
Goodwill	130	90
Equity affiliates	36	39
Intangible assets, net	102	96
Deferred income taxes	181	163
Other assets	175	58
Total assets	3,019	3,004
Current liabilities:
Short-term borrowings	13	33
Accounts payable and accrued liabilities	460	537
Income taxes payable	14	22
Current portion of long-term debt	7	7
Total current liabilities	494	599
Long-term debt	1,164	1,024
Deferred income taxes	41	41
Other liabilities	277	206
Commitments and contingencies (Note G)
Preferred stock:
Authorized: 2,000,000 shares of $1 par value Issued and Outstanding: None and none
Common stock:
Authorized: 200,000,000 shares of $1 par value Issued: 56,611,504 and 57,250,454 shares Outstanding: 56,460,448 and 57,080,589 shares	57	57
Less cost of 151,056 and 169,865 shares of common treasury stock	(4)	(5)
Retained earnings	1,277	1,337
Accumulated other comprehensive income (loss)	(400)	(391)
Total Cabot Corporation stockholders' equity	930	998
Noncontrolling interests	113	136
Total stockholders' equity	1,043	1,134
Total liabilities and stockholders' equity	$ 3,019	$ 3,004

Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 2	$ 3
Preferred stock, authorized shares	2,000,000	2,000,000
Preferred stock, par value	$ 1	$ 1
Preferred stock, Issued shares	0	0
Preferred stock, Outstanding shares	0	0
Common stock, authorized shares	200,000,000	200,000,000
Common stock, par value	$ 1	$ 1
Common stock, issued shares	56,611,504	57,250,454
Common stock, outstanding shares	56,460,448	57,080,589
Common treasury stock, shares	151,056	169,865

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows from Operating Activities:
Net income (loss)	$ 44	$ 146
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	117	110
Specialty Fluids loss on sale and asset impairment		28
Impairment of investment in equity affiliate		11
Deferred tax provision (benefit)	(20)	(20)
Employee benefit plan settlement		6
Equity in earnings of affiliated companies	(2)	(1)
Non-cash compensation	5	11
Other non-cash (income) expense	4	(2)
Cash dividends received from equity affiliates	1	2
Changes in assets and liabilities:
Accounts and notes receivable	172	6
Inventories	74	(14)
Prepaid expenses and other assets	(25)	(1)
Accounts payable and accrued liabilities	(68)	(65)
Income taxes payable	(10)	(24)
Other liabilities	(14)	(27)
Cash provided (used) by operating activities	278	166
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(162)	(155)
Proceeds from sale of business, net of cash held in escrow of $— and $5		130
Acquisitions of businesses, net of cash acquired of $1 and $—	(92)	(3)
Other	2	(5)
Cash provided (used) by investing activities	(252)	(33)
Cash Flows from Financing Activities:
Borrowings under financing arrangements		29
Proceeds from issuance (repayments) of commercial paper, net	(20)	(176)
Proceeds from long-term debt	444	344
Repayments of long-term debt	(334)	(75)
Repayments of redeemable preferred stock		(25)
Purchases of common stock	(44)	(144)
Proceeds from sales of common stock	3	2
Cash dividends paid to noncontrolling interests	(26)	(23)
Cash dividends paid to common stockholders	(60)	(60)
Cash provided (used) by financing activities	(37)	(146)
Repayments under financing arrangements		(18)
Effects of exchange rate changes on cash	4	(15)
Increase (decrease) in cash and cash equivalents	(7)	(28)
Cash and cash equivalents at beginning of period	169	175
Cash and cash equivalents at end of period	$ 162	$ 147

Consolidated Statements of Cash Flows (Parenthetical) (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Statement Of Cash Flows [Abstract]
Cash held in escrow related to sale of business		$ 5
Cash acquired in acquisition of business	$ 1

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Statement Of Stockholders Equity [Abstract]
Common stock, cash dividends paid, per share	$ 0.35	$ 0.35	$ 0.35	$ 0.33	$ 0.33	$ 0.33

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Common Stock, Net of Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Cabot Corporation Stockholders' Equity [Member]	Noncontrolling Interests [Member]
Beginning Balance at Sep. 30, 2018	$ 1,279	$ 54		$ 1,417	$ (317)	$ 1,154	$ 125
Beginning Balance, Shares at Sep. 30, 2018		60,367
Net income (loss)	77			69		69	8
Total other comprehensive income (loss)	(3)				(3)	(3)
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Issuance of stock under equity compensation plans, Shares		344
Amortization of share-based compensation	5		$ 5			5
Purchase and retirement of common stock	(62)	$ (1)	(5)	(56)		(62)
Purchase and retirement of common stock, Shares		(1,201)
Ending Balance at Dec. 31, 2018	1,276	$ 53		1,410	(320)	1,143	133
Ending Balance, Shares at Dec. 31, 2018		59,510
Beginning Balance at Sep. 30, 2018	1,279	$ 54		1,417	(317)	1,154	125
Beginning Balance, Shares at Sep. 30, 2018		60,367
Net income (loss)	146
Total other comprehensive income (loss)	6
Cash dividends paid, Common stock, per share	(60)
Ending Balance at Jun. 30, 2019	1,226	$ 52		1,351	(311)	1,092	134
Ending Balance, Shares at Jun. 30, 2019		57,759
Beginning Balance at Dec. 31, 2018	1,276	$ 53		1,410	(320)	1,143	133
Beginning Balance, Shares at Dec. 31, 2018		59,510
Net income (loss)	29			23		23	6
Total other comprehensive income (loss)	7				5	5	2
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Cash dividends declared to noncontrolling interests	(13)						(13)
Issuance of stock under equity compensation plans	1	$ 1				1
Issuance of stock under equity compensation plans, Shares		41
Amortization of share-based compensation	2		2			2
Purchase and retirement of common stock	(50)	$ (2)	(2)	(46)		(50)
Purchase and retirement of common stock, Shares		(1,101)
Ending Balance at Mar. 31, 2019	1,232	$ 52		1,367	(315)	1,104	128
Ending Balance, Shares at Mar. 31, 2019		58,450
Net income (loss)	40			32		32	8
Total other comprehensive income (loss)	2				4	4	(2)
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Issuance of stock under equity compensation plans, Shares		56
Amortization of share-based compensation	4		4			4
Purchase and retirement of common stock	(32)		(4)	(28)		(32)
Purchase and retirement of common stock, Shares		(747)
Ending Balance at Jun. 30, 2019	1,226	$ 52		1,351	(311)	1,092	134
Ending Balance, Shares at Jun. 30, 2019		57,759
Beginning Balance at Sep. 30, 2019	1,134	$ 52		1,337	(391)	998	136
Beginning Balance, Shares at Sep. 30, 2019		57,081
Adoption of accounting standards				3	(3)
Net income (loss)	46			41		41	5
Total other comprehensive income (loss)	43				40	40	3
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Cash dividends declared to noncontrolling interests	(19)						(19)
Issuance of stock under equity compensation plans	1		1			1
Issuance of stock under equity compensation plans, Shares		273
Amortization of share-based compensation	1		1			1
Purchase and retirement of common stock	(34)		(2)	(32)		(34)
Purchase and retirement of common stock, Shares		(699)
Ending Balance at Dec. 31, 2019	1,152	$ 52		1,329	(354)	1,027	125
Ending Balance, Shares at Dec. 31, 2019		56,655
Beginning Balance at Sep. 30, 2019	1,134	$ 52		1,337	(391)	998	136
Beginning Balance, Shares at Sep. 30, 2019		57,081
Net income (loss)	44
Total other comprehensive income (loss)	(4)
Cash dividends paid, Common stock, per share	(60)
Ending Balance at Jun. 30, 2020	1,043	$ 53		1,277	(400)	930	113
Ending Balance, Shares at Jun. 30, 2020		56,460
Beginning Balance at Dec. 31, 2019	1,152	$ 52		1,329	(354)	1,027	125
Beginning Balance, Shares at Dec. 31, 2019		56,655
Net income (loss)	3			(1)		(1)	4
Total other comprehensive income (loss)	(78)				(75)	(75)	(3)
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Cash dividends declared to noncontrolling interests	(16)						(16)
Issuance of stock under equity compensation plans	2		2			2
Issuance of stock under equity compensation plans, Shares		30
Amortization of share-based compensation	2		2			2
Purchase and retirement of common stock	(10)		(4)	(6)		(10)
Purchase and retirement of common stock, Shares		(241)
Ending Balance at Mar. 31, 2020	1,035	$ 52		1,302	(429)	925	110
Ending Balance, Shares at Mar. 31, 2020		56,444
Net income (loss)	(5)			(6)		(6)	1
Total other comprehensive income (loss)	31				29	29	2
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Issuance of stock under equity compensation plans		$ 1	(1)
Issuance of stock under equity compensation plans, Shares		18
Amortization of share-based compensation	2		2			2
Purchase and retirement of common stock			$ (1)	1
Purchase and retirement of common stock, Shares		(2)
Ending Balance at Jun. 30, 2020	$ 1,043	$ 53		$ 1,277	$ (400)	$ 930	$ 113
Ending Balance, Shares at Jun. 30, 2020		56,460

Basis of Presentation

9 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Basis of Presentation

A. Basis of Presentation

The consolidated financial statements have been prepared in conformity with accounting policies generally accepted in the United States (“U.S.”) and include the accounts of Cabot Corporation (“Cabot” or the “Company”) and its wholly owned subsidiaries and majority-owned and controlled U.S. and non-U.S. subsidiaries. Additionally, Cabot considers consolidation of entities over which control is achieved through means other than voting rights. Intercompany transactions have been eliminated in consolidation.

The unaudited consolidated financial statements have been prepared in accordance with the requirements of Form 10-Q and consequently do not include all disclosures required by Form 10-K. Additional information may be obtained by referring to Cabot’s Annual Report on Form 10-K for its fiscal year ended September 30, 2019 (“2019 10-K”).

The financial information submitted herewith is unaudited and reflects all adjustments which are, in the opinion of management, necessary to provide a fair statement of the results for the interim periods ended June 30, 2020 and 2019. All such adjustments are of a normal recurring nature. The results for interim periods are not necessarily indicative of the results to be expected for the fiscal year.

Effective October 1, 2019, the Company adopted the accounting standard for leases issued by the Financial Accounting Standards Board (“FASB”) in February 2016.

As discussed in Note C, effective April 1, 2020, the Company acquired Shenzhen Sanshun Nano New Materials Co., Ltd (“SUSN”), a leading carbon nanotube producer. The results of operations, and cash flows, of SUSN are included in the Company’s consolidated financial statements from the date of acquisition.

Significant Accounting Policies

9 Months Ended

Jun. 30, 2020

Accounting Policies [Abstract]

Significant Accounting Policies

B. Significant Accounting Policies

Revenue Recognition

Cabot recognizes revenue when its customers obtain control of promised goods or services. The revenue recognized is the amount of consideration that the Company expects to receive in exchange for those goods or services. The Company’s contracts with customers are generally for products only and do not include other performance obligations. Generally, Cabot considers purchase orders, which in some cases are governed by master supply agreements, to be contracts with customers. The transaction price as specified on the purchase order or sales contract is considered the standalone selling price for each distinct product. To determine the transaction price at the time when revenue is recognized, the Company evaluates whether the price is subject to adjustments, such as for returns, discounts or volume rebates, which are stated in the customer contract, to determine the net consideration to which the Company expects to be entitled. Revenue from product sales is recognized based on a point in time model when control of the product is transferred to the customer, which typically occurs upon shipment or delivery of the product to the customer and title, risk and rewards of ownership have passed to the customer. The Company has an immaterial amount of revenue that is recognized over time. Payment terms typically range from zero to ninety days.

Shipping and handling costs incurred after the transfer of control of a product to the customer are billed to the customer and are recorded as sales revenue, as the Company considers these to be fulfillment costs. Shipping and handling costs are expensed in the period incurred and included in Cost of sales within the Consolidated Statement of Operations. Taxes collected on sales to customers are excluded from the transaction price.

The Company generally provides a warranty that its products will substantially conform to the identified specifications. The Company’s liability typically is limited to either a credit equal to the purchase price or replacement of the non-conforming product. Returns under warranty have historically been immaterial.

The Company does not have contract assets or liabilities that are material.

As permitted by the FASB’s revenue recognition standard, Revenue from Contracts with Customers, when the period of time between the transfer of control of the goods and the time the customer pays for the goods is one year or less, the Company does not consider there to be a significant financing component associated with the contract.

Intangible Assets and Goodwill Impairment

The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for assets acquired and liabilities assumed in an acquisition are allocated to the assets and liabilities based on their fair values at the date of acquisition. The Company uses assumptions and estimates in determining the fair value of assets acquired and liabilities assumed in a business combination. The determination of the fair value of intangible assets requires the use of significant judgment with regard to assumptions used in the valuation model. The Company estimates the fair value of identifiable acquisition-related intangible assets principally based on projections of cash flows that will arise from these assets. The projected cash flows are discounted to determine the fair value of the assets at the dates of acquisition.

Definite-lived intangible assets, which are comprised of trademarks, customer relationships and developed technologies, are amortized over their estimated useful lives and are reviewed for impairment when indication of potential impairment exists, such as a significant reduction in cash flows associated with the assets.

Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value assigned to the net tangible and identifiable intangible assets acquired. Goodwill is not amortized, but is reviewed for impairment annually as of August 31, or when events or changes in the business environment indicate that the carrying value of the reporting unit may exceed its fair value. A reporting unit, for the purpose of the impairment test, is at or below the operating segment level, and constitutes a business for which discrete financial information is available and regularly reviewed by segment management. Reinforcement Materials, and the fumed metal oxides, specialty compounds and specialty carbons product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of June 30, 2020.

For the purpose of the goodwill impairment test, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value, an additional quantitative evaluation is performed. Alternatively, the Company may elect to proceed directly to the quantitative goodwill impairment test. If based on the quantitative evaluation the fair value of the reporting unit is less than its carrying amount, a goodwill impairment loss would result. The goodwill impairment loss would be the amount by which the carrying value of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. The fair value of a reporting unit is based on discounted estimated future cash flows. The fair value is also benchmarked against a market approach using the guideline public company method. The assumptions used to estimate fair value include management’s best estimates of future growth rates, operating cash flows, capital expenditures and discount rates over an estimate of the remaining operating period at the reporting unit level. Based on the Company’s most recent annual goodwill impairment test performed as of August 31, 2019, the fair values of the Reinforcement Materials, Fumed Metal Oxides and Specialty Compounds reporting units were substantially in excess of their carrying values.

Long-lived Assets Impairment

The Company’s long-lived assets primarily include property, plant and equipment, intangible assets and long-term investments. The carrying values of long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable.

To test for impairment of assets, the Company generally uses a probability-weighted estimate of the future undiscounted net cash flows of the assets over their remaining lives to determine if the value of the asset is recoverable. Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable.

An asset impairment is recognized when the carrying value of the asset is not recoverable based on the analysis described above, in which case the asset is written down to its fair value. If the asset does not have a readily determinable fair value, a discounted cash flow model may be used to determine the fair value of the asset. In circumstances when an asset does not have separately identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset.

The Company continues to consider strategic options for its Purification Solutions business. Depending on the actions taken, there could be a negative impact on the fair value of the Purification Solutions reporting unit, which may lead to an impairment.

Property, Plant and Equipment

Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The depreciable lives for buildings, machinery and equipment, and other fixed assets are between twenty and twenty-five years, ten and twenty-five years, and three and twenty-five years, respectively. The cost and accumulated depreciation for property, plant and equipment sold, retired, or otherwise disposed of are removed from the Consolidated Balance Sheets and resulting gains or losses are included in earnings in the Consolidated Statements of Operations. Expenditures for repairs and maintenance are charged to expenses as incurred. Expenditures for major renewals and betterments, which significantly extend the useful lives of existing plant and equipment, are capitalized and depreciated.

Income Tax in Interim Periods

The Company records its tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period.

Valuation allowances are provided against the future tax benefits that arise from the deferred tax assets in jurisdictions for which no benefit can be recognized. The estimated annual effective tax rate may be significantly impacted by nondeductible expenses and the Company’s projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised.

Inventory Valuation

Inventories are stated at the lower of cost or net realizable value. The cost of inventory is determined using the FIFO method.

Cabot periodically reviews inventory for both potential obsolescence and potential declines in anticipated selling prices. In this review, the Company makes assumptions about the future demand for and market value of the inventory, and based on these assumptions estimates the amount of any obsolete, unmarketable, slow moving, or overvalued inventory. Cabot writes down the value of these inventories by an amount equal to the difference between the cost of the inventory and its estimated net realizable value.

Pensions and Other Postretirement Benefits

The Company recognizes the funded status of defined benefit pension and other postretirement benefit plans as an asset or liability. This amount is defined as the difference between the fair value of plan assets and the benefit obligation. Pension and post-retirement benefit costs other than service cost are included in Other income (expense) in the Consolidated Statement of Operations. The Company is required to recognize as a component of Other comprehensive income (loss), net of tax, the actuarial gains/losses and prior service costs/credits that arise but were not previously required to be recognized as components of net periodic benefit cost. Other comprehensive income (loss) is adjusted as these amounts are later recognized in income as components of net periodic benefit cost.

Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) (“AOCI”), which is included as a component of stockholders’ equity, includes unrealized gains or losses on derivative instruments, currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments.

Recently Adopted Accounting Standards

In February 2016, the FASB issued a new standard for the accounting for leases. This standard requires lessees to recognize assets and liabilities for most leases, but recognize expenses on their income statements in a manner that is similar to the historical accounting treatment for leases. The Company adopted the standard on October 1, 2019 using the modified retrospective optional transition method. Accordingly, leases in the prior period continue to be reported and disclosed in accordance with the Company’s historical accounting treatment. The Company elected the package of practical expedients that permits the Company to not reassess the identification, classification and initial direct costs of leases commencing before the October 1, 2019 effective date and to exclude short-term leases from the balance sheet. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases or the practical expedient to not separate lease and non-lease components to existing leases, as well as new leases, through transition. The Company allocates the total consideration to the lease components and non-lease components on an observable stand-alone price basis to all asset classes.

Adoption of the new lease standard resulted in the recognition of operating lease right-of-use (“ROU”) assets and operating lease liabilities of approximately $106 million and $111 million, respectively, as of October 1, 2019. Refer to Note H for further

details regarding the balance sheet classification of these items. The difference between the operating lease ROU assets and operating lease liabilities reflects the reclassification of historical deferred rent balances of approximately $5 million. The effects of transition to the new standard resulted in no cumulative adjustment to retained earnings in the period of adoption. The standard did not materially impact the Company’s Consolidated Statement of Operations or Consolidated Statement of Cash Flows. The new standard did not have a material impact on the Company’s liquidity or debt-covenant compliance as of adoption.

In February 2018, the FASB issued a new standard that allows entities to reclassify from Accumulated other comprehensive income (loss) (“AOCI”) to Retained earnings stranded tax effects resulting from changes made as a result of the Tax Cuts and Jobs Act of 2017 (the “Act”). The Company adopted this standard on October 1, 2019 which resulted in the reclassification of a $2 million net gain from AOCI to Retained earnings. The reclassification was primarily related to the Company’s pension plans and derivative instruments.

Recent Accounting Pronouncements

In June 2016, the FASB issued a new standard on measurement of credit losses. The standard introduces an "expected loss" impairment model that applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables and other financial assets. Entities are required to estimate expected credit losses over the life of financial assets and record an allowance against the assets’ amortized cost basis to present them at the amount expected to be collected. The new standard is effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The Company will adopt this standard effective October 1, 2020. The Company does not expect the adoption of this standard to materially impact the Company’s consolidated financial statements.

In March 2020, the FASB issued a new standard on Reference Rate Reform, which provides temporary optional expedients and exceptions to the existing guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate ("LIBOR") and other interbank offered rates to alternative reference rates. The standard was effective upon issuance and may generally be applied through December 31, 2022 to any new or amended contracts, hedging relationships, and other transactions that reference LIBOR. The Company is currently evaluating the timing of adoption and the impact of the adoption of this standard on its consolidated financial statements.

Acquisitions and Divestitures

9 Months Ended

Jun. 30, 2020

Business Combinations [Abstract]

Acquisitions and Divestitures

C. Acquisitions and Divestitures

Acquisitions

NSCC Carbon (Jiangsu) Co. Ltd

In September 2018, the Company acquired NSCC Carbon (Jiangsu) Co. Ltd, a carbon black manufacturing facility in Pizhou, Jiangsu Province, China for a purchase price of $8 million, subject to certain conditions. The purchase price conditions were satisfied in September 2019 and the purchase price was paid in the first quarter of fiscal 2020. The Company has commenced plans to modify this facility to produce specialty carbons and therefore the plant is temporarily mothballed. The modifications are expected to be completed, and production is expected to commence, in 2022. Transition-related costs associated with this acquisition were $1 million and $2 million for the three and nine months ended June 30, 2020, respectively, and $1 million and $4 million for the three and nine months ended June 30, 2019, respectively.

Shenzhen Sanshun Nano New Materials Co., Ltd

On April 1, 2020, the Company purchased Shenzhen Sanshun Nano New Materials Co., Ltd (SUSN), a leading carbon nanotube producer, for an estimated purchase price of $100 million, consisting of: (i) cash consideration of $84 million, net of $1 million acquired (ii) contingent consideration of $3 million to be paid over the two-year period ending March 31, 2022 upon the satisfaction of certain milestones, and (iii) the assumed debt of $13 million. The debt the Company assumed in the transaction was repaid in June 2020. The operating results of SUSN were included in the results of the Company's Performance Chemicals segment beginning in the third quarter of fiscal 2020, and totaled approximately $6 million of revenue in the quarter.

The Company incurred acquisition and integration costs of $2 million through June 30, 2020 associated with the transaction, which are included in Selling and administrative expenses and Cost of Sales in the Consolidated Statements of Operations.

The provisional allocation of the purchase price set forth below was based on estimates of the fair value of assets acquired and liabilities assumed as of April 1, 2020.

	(In millions)
Assets
Cash	$	1
Accounts Receivable		8
Inventories		4
Prepaid expenses and other current assets		2
Property, plant and equipment		38
Intangible assets		15
Goodwill		45
Deferred tax asset		1
Other assets		2
Total assets acquired		116

Liabilities
Accounts payable and accrued liabilities		(12	)
Income taxes payable		(2	)
Long-term debt		(13	)
Other liabilities		(4	)

Total liabilities assumed		(31	)

Cash consideration paid	$	85

As part of the purchase price allocation, the Company determined the separately identifiable intangible assets are comprised of developed technologies of $9 million, which will be amortized over 10 years, customer relationships of $4 million, which will be amortized over 20 years, and trademarks of $2 million, which will be amortized over 10 years. The Company estimated the fair values of the identifiable acquisition-related intangible assets based on projections of cash flows that will arise from those assets. The projected cash flows were discounted to determine the fair value of the assets at the date of acquisition. The determination of the fair value of the intangible assets acquired required the use of judgment with regard to assumptions in the discounted cash flow model used and determination of the useful lives of the developed technologies, customer relationships and trademarks.

The excess of the purchase price over the fair value of the tangible net assets and intangible assets acquired was recorded as goodwill. The goodwill recognized is attributable to the growth and operating synergies that the Company expects to realize from this acquisition. Goodwill generated from the acquisition will not be deductible for tax purposes.

Divestitures

Sale of Specialty Fluids Business

In June 2019, the Company completed the sale of its Specialty Fluids business, an operating segment of the Company, to Sinomine (Hong Kong) Rare Metals Resource Co. Limited, a wholly owned subsidiary of Sinomine Resource Group Co., Ltd. (“Sinomine”), for total proceeds of $133 million. The Company recognized a $20 million impairment charge during the second quarter of fiscal 2019 and a pre-tax loss on the sale of the Specialty Fluids business of $9 million in fiscal 2019. The sale was subject to customary post-closing adjustments, which were finalized during the second quarter of fiscal 2020 and resulted in an additional pre-tax loss on sale of $1 million.

Employee Benefit Plans

9 Months Ended

Jun. 30, 2020

Compensation And Retirement Disclosure [Abstract]

Employee Benefit Plans

D. Employee Benefit Plans

Net periodic defined benefit pension costs include the following:

	Three Months Ended June 30
	2020						2019
	Pension Benefits
	U.S.			Foreign			U.S.			Foreign
	(In millions)
Service cost	$	—		$	1		$	1		$	2
Interest cost		1			1			1			1
Expected return on plan assets		(1	)		(2	)		(2	)		(2	)
Amortization of prior service costs (credit)		—			—			—			2
Amortization of actual loss		—			1			—			1
Net periodic benefit (credit) cost	$	—		$	1		$	—		$	4

	Nine Months Ended June 30
	2020						2019
	Pension Benefits
	U.S.			Foreign			U.S.			Foreign
	(In millions)
Service cost	$	1		$	4		$	1		$	5
Interest cost		3			3			4			4
Expected return on plan assets		(3	)		(7	)		(7	)		(8	)
Amortization of prior service cost (credit)		—			—			—			2
Amortization of actuarial loss		—			2			—			2
Settlement and curtailment gain		—			—			—			(6	)
Net periodic benefit (credit) cost	$	1		$	2		$	(2	)	$	(1	)

Other postretirement benefit costs were less than $1 million and $1 million for the three and nine months ended June 30, 2020, respectively. Other postretirement benefit gains were less than $1 million for both the three and nine months ended June 30, 2019.

U.S. Cash Balance Plan Termination

In fiscal 2019, the Company’s Board of Directors approved a resolution to terminate the Company’s U.S. pension plan. The Company commenced the U.S. plan termination process during the third quarter of fiscal 2019 and expects to complete the transfer of the U.S. plan’s assets to participants by the end of calendar year 2020. The pension liability will be settled through a combination of lump-sum payments and purchased annuities. Upon settlement of the benefit liabilities accrued in the plan, the Company will recognize a loss associated with the release of approximately $13 million from AOCI in the Consolidated Balance Sheet to Other income (expense) in the Consolidated Statement of Operations and will also recognize in Other income (expense) any additional gain or loss between the fair value of plan assets and the benefit plan liability on the date of settlement.

Curtailments and Settlements of Employee Benefit Plans

In fiscal 2019, the Company transferred the majority of the defined benefit obligations and pension plan assets in one of its foreign defined benefit plans to a multi-employer plan. This action moved the administrative, asset custodial, asset investment, actuarial, communication and benefit payment obligations to the multi-employer fund administrator. As a result of the transfer, a pre-tax gain of $6 million was recorded in the first quarter of fiscal 2019, which is included in Other income (expense) in the Consolidated Statement of Operations. In addition, as part of the transfer, the Company recorded a $3 million charge in the first quarter of fiscal 2019 reflecting the Company’s agreement to fund the actuarial loss gap between the terminated plan and the multi-employer plan. This charge is included in Other income (expense) in the Consolidated Statement of Operations.

- Definition

The entire disclosure for retirement benefits.

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+ Details

Goodwill and Intangible Assets

9 Months Ended

Jun. 30, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

E. Goodwill and Intangible Assets

The carrying amount of goodwill attributable to each reportable segment with goodwill balances and the changes in those balances during the nine month period ended June 30, 2020 are as follows:

	Reinforcement Materials			Performance Chemicals		Total
	(In millions)
Balance at September 30, 2019	$	50		$	40	$	90
Goodwill acquired⁽¹⁾		—			45		45
Foreign currency impact		(5	)		—		(5	)
Balance at June 30, 2020	$	45		$	85	$	130

⁽¹⁾Consists of goodwill acquired in the acquisition of SUSN as described in Note C.

The following table provides information regarding the Company’s intangible assets:

	June 30, 2020							September 30, 2019
	Gross Carrying Value		Accumulated Amortization			Net Intangible Assets		Gross Carrying Value		Accumulated Amortization			Net Intangible Assets
	(In millions)
Intangible assets with finite lives
Developed technologies	$	58	$	(7	)	$	51	$	50	$	(5	)	$	45
Trademarks		11		(1	)		10		8		—			8
Customer relationships		54		(13	)		41		57		(14	)		43
Total intangible assets⁽¹⁾	$	123	$	(21	)	$	102	$	115	$	(19	)	$	96

⁽¹⁾Total intangible assets as of June 30, 2020 includes $15 million of intangible assets from the acquisition of SUSN as described in Note C and an unfavorable impact of foreign currency translation of $4 million.

Intangible assets are amortized over their estimated useful lives, which range between ten and twenty-five years, with a weighted average amortization period of approximately eighteen years. Amortization expense for the three months ended June 30, 2020 and 2019 was $2 million and $1 million, respectively, and for the nine months ended June 30, 2020 and 2019 was $5 million and $4 million, respectively. Amortization expense is included in Cost of sales, Selling and administrative expenses, and Research and technical expenses in the Consolidated Statements of Operations.  Total amortization expense is estimated to be approximately $7 million each year for the next five fiscal years.

Accumulated Other Comprehensive Income (Loss)

9 Months Ended

Jun. 30, 2020

Stockholders Equity Note [Abstract]

Accumulated Other Comprehensive Income (Loss)

F. Accumulated Other Comprehensive Income (Loss)

Comprehensive income combines net income (loss) and other comprehensive income items, which are reported as components of stockholders’ equity in the accompanying Consolidated Balance Sheets.

Changes in each component of AOCI, net of tax, were as follows:

	Currency Translation Adjustment			Unrealized Gains on Investments			Pension and Other Postretirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2019, attributable to Cabot Corporation	$	(338	)	$	1		$	(54	)	$	(391	)
Other comprehensive income (loss) before reclassifications		43			—			—			43
Amounts reclassified from AOCI		(1	)		—			1			—
Adoption of accounting standards		(3	)		(1	)		1			(3	)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		3			—			—			3
Balance at December 31, 2019, attributable to Cabot Corporation		(302	)		—			(52	)		(354	)
Other comprehensive income (loss) before reclassifications		(78	)		—			—			(78	)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		(3	)		—			—			(3	)
Balance at March 31, 2020, attributable to Cabot Corporation		(377	)		—			(52	)		(429	)
Other comprehensive income (loss) before reclassifications		31			—			(1	)		30
Amounts reclassified from AOCI		(1	)		—			2			1
Less: Other comprehensive income (loss) attributable to noncontrolling interests		2			—			—			2
Balance at June 30, 2020, attributable to Cabot Corporation	$	(349	)	$	—		$	(51	)	$	(400	)

The amounts reclassified out of AOCI and into the Consolidated Statements of Operations in the three and nine months ended June 30, 2020 and 2019 were as follows:

	Affected Line Item in the Consolidated	Three Months Ended June 30						Nine Months Ended June 30
	Statements of Operations	2020			2019			2020			2019
		(In millions)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense	Interest expense	$	(2	)	$	(1	)	$	(4	)	$	(4	)
(Gains) losses excluded from effectiveness testing and amortized to interest expense	Interest expense		—			—			1			1
Pension and other postretirement
Amortization of actuarial losses and prior service cost (credit)	Net Periodic Benefit Cost - see Note D for details		2			2			3			2
Settlement and curtailment gain	Net Periodic Benefit Cost - see Note D for details		—			—			—			(6	)
Total before tax			—			1			—			(7	)
Tax impact	Provision (benefit) for income taxes		1			1			1			(2	)
Total after tax		$	1		$	2		$	1		$	(9	)

Commitments and Contingencies

9 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

G. Commitments and Contingencies

Contingencies

Respirator Liabilities

Cabot has exposure in connection with a safety respiratory products business that a subsidiary acquired from American Optical Corporation (“AO”) in an April 1990 asset purchase transaction. The subsidiary manufactured respirators under the AO brand and disposed of that business in July 1995. In connection with its acquisition of the business, the subsidiary agreed, in certain circumstances, to assume a portion of AO’s liabilities, including costs of legal fees together with amounts paid in settlements and judgments, allocable to AO respiratory products used prior to the 1990 purchase by the Cabot subsidiary. In exchange for the subsidiary’s assumption of certain of AO’s respirator liabilities, AO agreed to provide to the subsidiary the benefits of: (i) AO’s insurance coverage for the period prior to the 1990 acquisition and (ii) a former owner’s indemnity of AO holding it harmless from any liability allocable to AO respiratory products used prior to May 1982. As more fully described in the 2019 10-K, the respirator liabilities generally involve claims for personal injury, including asbestosis, silicosis and coal worker’s pneumoconiosis, allegedly resulting from the use of respirators that are alleged to have been negligently designed and/or labeled. Neither Cabot, nor its past or present subsidiaries, at any time manufactured asbestos or asbestos-containing products. At no time did this respiratory product line represent a significant portion of the respirator market. In addition to Cabot’s subsidiary, other parties are responsible for significant portions of the costs of these respirator liabilities (as defined in the 2019 10-K, the “Payor Group”).

On February 28, 2020, Cabot, with certain members of the Payor Group, entered into a settlement agreement resolving a large group of claims, including claims alleging serious injury, brought by coal workers in Kentucky and West Virginia represented by common legal counsel. The Company’s share of this liability is $65.2 million, and during the second quarter of fiscal 2020, Cabot recorded a charge of $50 million for this settlement, which was included in Selling and administrative expenses in the Consolidated Statements of Operations. The Company paid $32.6 million of the settlement during the third quarter of fiscal 2020 and the remaining $32.6 million, which is included in Accounts payable and accrued liabilities on the Consolidated Balance Sheets as of June 30, 2020, will be paid in the first quarter of fiscal 2021.

In addition to the February 2020 settlement, Cabot has a reserve to cover its expected share of liabilities for existing and future respirator liability claims, which is included in Other liabilities and Accounts payable and accrued liabilities on the Consolidated Balance Sheets. The Company expects these liabilities to be incurred over a number of years. The reserve was $21 million and $35 million as of June 30, 2020 and September 30, 2019, respectively. The Company’s current estimate of the cost of its share of existing and future respirator liability claims is based on facts and circumstances existing at this time, including the nature of the remaining claims. Because reserves are limited to amounts that are probable and estimable as of a relevant measurement date, and there is inherent difficulty in projecting the impact of potential developments on Cabot’s share of liability for these existing and future claims, the actual amount of liabilities related to these claims could be different from Cabot’s reserve.

Developments that could affect the Company’s estimate include, but are not limited to, (i) significant changes in the number of future claims, (ii) changes in the rate of dismissals without payment of pending claims, (iii) significant changes in the average cost of resolving claims, including potential settlements of groups of claims, (iv) significant changes in the legal costs of defending these claims, (v) changes in the nature of claims received, (vi) trial and appellate outcomes, (vii) changes in the law and procedure applicable to these claims, (viii) the financial viability of the parties that contribute to the settlement of respirator claims, (ix) exhaustion of the insurance coverage maintained by certain of the parties that contribute to the settlement of respirator claims, or a change in the availability of the indemnity provided by a former owner of the business, (x) changes in the allocation of costs among the various parties paying legal and settlement costs, and (xi) a determination that the assumptions that were used to estimate Cabot’s share of liability are no longer reasonable.

Other Matters

The Company has various other lawsuits, claims and contingent liabilities arising in the ordinary course of its business and with respect to its divested businesses. The Company does not believe that any of these matters will have a material adverse effect on its financial position; however, litigation is inherently unpredictable. Cabot could incur judgments, enter into settlements or revise its expectations regarding the outcome of certain matters, and such developments could have a material impact on its results of operations in the period in which the amounts are accrued or its cash flows in the period in which the amounts are paid.

Leases

9 Months Ended

Jun. 30, 2020

Leases [Abstract]

Leases

H. Leases

The Company determines if an arrangement is a lease at inception. The Company considers a contract to be or to contain a lease if the contract conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration.

A lease liability is recorded at commencement for the net present value of future lease payments over the lease term. The discount rate used is generally the Company’s estimated incremental borrowing rate based on credit-adjusted and term-specific discount rates, using a third-party yield curve. An ROU asset is recorded and recognized at commencement at the lease liability amount, including initial direct costs incurred, and is reduced for lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option.

In the normal course of its business, the Company enters into various leases as the lessee, primarily related to certain transportation vehicles, warehouse facilities, office space, and machinery and equipment. These leases have remaining lease terms between one and nineteen years, some of which may include options to extend the leases for up to fifteen years or options to terminate the leases. The Company’s land leases have remaining lease terms up to seventy years.

Some lease arrangements require variable payments that are dependent on usage, output, or index-based adjustments. The Company does not have material variable lease payments.

The Company has elected not to recognize short-term leases on the balance sheet for all underlying asset classes. Short-term leases are leases that, at the commencement date, have a lease term of twelve months or less and do not include a purchase option that the Company is reasonably certain to exercise. Short-term leases are expensed on a straight-line basis over the lease term.

The components of the Company’s lease costs were as follows:

	Three Months Ended June 30		Nine Months Ended June 30
	2020		2020
	(In millions)
Operating lease cost	$	7	$	24
Finance lease cost		2		4
Total lease cost	$	9	$	28

For the three and nine months ended June 30, 2020, short-term lease costs were $1 million and $5 million, respectively. For both the three and nine months ended June 30, 2020, variable lease costs were less than $1 million.

Supplemental cash flow information related to the Company’s leases was as follows:

	Three Months Ended June 30		Nine Months Ended June 30
	2020		2020
	(In millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	7	$	19
Operating cash flows from finance leases		—		1
Financing cash flows from finance leases		1		2
Right-of-use assets obtained in exchange for new operating lease liabilities	$	8	$	13
Right-of-use assets obtained in exchange for new finance lease liabilities	$	—	$	23

Supplemental balance sheet information related to the Company’s leases was as follows:

Description	Balance Sheet Classification	June 30, 2020
		(In millions)
Lease ROU assets:
Operating	Other assets	$	102
Finance	Net property, plant and equipment		45
Total lease ROU assets		$	147

Lease liabilities:
Current:
Operating	Accounts payable and accrued liabilities	$	17
Finance	Current portion of long-term debt		3
Long-term:
Operating	Other liabilities		91
Finance	Long-term debt		28
Total lease liabilities		$	139

The following table presents the weighted-average remaining lease term and discount rates for the Company’s leases as of June 30, 2020:

Description	June 30, 2020
Weighted-average remaining lease term (years):
Operating leases		16
Finance leases		12
Weighted-average discount rate:
Operating leases		2.21	%
Finance leases		4.44	%

Future minimum lease payments under non-cancelable operating and finance leases as of June 30, 2020 were as follows:

Years Ended September 30	Operating leases		Finance leases
	(In millions)
Remainder of fiscal 2020	$	6	$	1
2021		16		5
2022		12		4
2023		10		4
2024		10		4
2025 and thereafter		75		25
Total lease payments		129		43
Less: imputed interest		21		12
Total	$	108	$	31

The Company’s future minimum lease payments under noncancelable leases as of September 30, 2019 were as follows:

Years Ended September 30	Operating leases		Capital leases
	(In millions)
2020	$	23	$	3
2021		14		3
2022		9		3
2023		9		3
2024		8		2
2025 and thereafter		68		7
Total lease payments		131		21
Less: imputed interest		—		9
Total	$	131	$	12

Income Tax

9 Months Ended

Jun. 30, 2020

Income Tax Disclosure [Abstract]

Income Tax

I. Income Tax

Effective Tax Rate

	Three Months Ended June 30						Nine Months Ended June 30
	2020			2019			2020			2019
	(Dollars in millions)
(Provision) benefit for income taxes	$	5		$	(30	)	$	(9	)	$	(43	)
Effective tax rate		51	%		43	%		17	%		23	%

For the three and nine months ended June 30, 2020, the (Provision) benefit for income taxes included a net discrete tax benefit of $2 million and $14 million, respectively. The $14 million was comprised of $8 million related to changes in uncertain tax positions and $6 million related to the impacts of Switzerland tax reform legislation. For the three and nine months ended June 30, 2019, the (Provision) benefit for income taxes included a net discrete tax expense of $13 million and a net discrete tax benefit of $11 million, respectively. Of these amounts, a net tax expense of $17 million and a nil amount, respectively, are related to U.S. tax reform legislation.

Uncertainties

Cabot and certain subsidiaries are under audit in a number of jurisdictions. In addition, certain statutes of limitations are scheduled to expire in the near future. It is reasonably possible that a further change in the unrecognized tax benefits may also occur within the next twelve months related to the settlement of one or more of these audits or the lapse of applicable statutes of limitations. However, an estimated range of the impact on the unrecognized tax benefits cannot be quantified at this time.

Cabot files U.S. federal and state and non-U.S. income tax returns in jurisdictions with varying statutes of limitations. The 2016 through 2019 tax years generally remain subject to examination by the IRS and various tax years from 2005 through 2019 remain subject to examination by the respective state tax authorities. In significant non-U.S. jurisdictions, various tax years from 2003 through 2019 remain subject to examination by their respective tax authorities. As of June 30, 2020, Cabot’s significant non-U.S. jurisdictions include Canada, China, France, Germany, Italy, Japan, Switzerland and the Netherlands.

During the three and nine months ended June 30, 2020, Cabot released uncertain tax positions of $3 million and $11 million, respectively, due to audit settlements and the expiration of statutes of limitations in various jurisdictions. During the three and nine months ended June 30, 2019, Cabot released uncertain tax positions of $1 million and $9 million, respectively, due to audit settlements and the expiration of statutes of limitations in various jurisdictions.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Earnings Per Share

9 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Earnings Per Share

J. Earnings Per Share

The following tables summarize the components of the basic and diluted earnings (loss) per common share (“EPS”) computations:

	Three Months Ended June 30					Nine Months Ended June 30
	2020			2019		2020		2019
	(In millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to Cabot Corporation	$	(6	)	$	32	$	34	$	124
Less: Dividends and dividend equivalents to participating securities		—			—		—		—
Earnings (loss) allocated to common shareholders (numerator)	$	(6	)	$	32	$	34	$	124

Weighted average common shares and participating securities outstanding		57.2			59.0		57.4		59.9
Less: Participating securities⁽¹⁾		0.7			0.8		0.7		0.8
Adjusted weighted average common shares (denominator)		56.5			58.2		56.7		59.1

Earnings (loss) per common share - basic:	$	(0.12	)	$	0.55	$	0.59	$	2.08

Diluted EPS:
Earnings (loss) allocated to common shareholders	$	(6	)	$	32	$	34	$	124
Plus: Earnings allocated to participating securities		—			—		—		1
Less: Adjusted earnings allocated to participating securities⁽²⁾		—			—		—		1
Earnings (loss) allocated to common shareholders (numerator)	$	(6	)	$	32	$	34	$	124

Adjusted weighted average common shares outstanding		56.5			58.2		56.7		59.1
Effect of dilutive securities:
Common shares issuable⁽³⁾		—			0.2		—		0.1
Adjusted weighted average common shares (denominator)		56.5			58.4		56.7		59.2

Earnings (loss) per common share - diluted:	$	(0.12	)	$	0.55	$	0.59	$	2.08

⁽¹⁾

^{Participating securities consist of shares underlying: (i) achieved but unvested performance-based restricted stock units, and (ii) unvested time-based restricted stock units. The holders of these units are entitled to receive dividend equivalents payable in cash to the extent dividends are paid on the Company’s outstanding common stock and equal in value to the dividends that would have been paid in respect of the shares underlying such units.}

Undistributed earnings are the earnings which remain after dividends declared during the period are assumed to be distributed to the common and participating shareholders. Undistributed earnings are allocated to common and participating shareholders on the same basis as dividend distributions. The calculation of undistributed earnings is as follows:

	Three Months Ended June 30					Nine Months Ended June 30
	2020			2019		2020			2019
	(In millions)
Calculation of undistributed earnings (loss):
Net income (loss) attributable to Cabot Corporation	$	(6	)	$	32	$	34		$	124
Less: Dividends declared on common stock		20			20		60			60
Less: Dividends declared on participating securities		—			—		—			—
Undistributed earnings (loss)	$	(26	)	$	12	$	(26	)	$	64

Allocation of undistributed earnings (loss):
Undistributed earnings (loss) allocated to common shareholders	$	(26	)	$	12	$	(26	)	$	64
Undistributed earnings allocated to participating shareholders		—			—		—			—
Undistributed earnings (loss)	$	(26	)	$	12	$	(26	)	$	64

⁽²⁾	Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (3) below, and then reallocated to participating securities.

⁽³⁾

Represents incremental shares of common stock from the (i) assumed exercise of stock options issued under Cabot’s equity incentive plans; and (ii) assumed issuance of shares to employees pursuant to the Company’s Deferred Compensation and Supplemental Retirement Plan. For the nine months ended June 30, 2020, 1,223,055 incremental shares of common stock were excluded from the calculation of diluted earnings per share because the inclusion of these shares would have been antidilutive. For the three months ended June 30, 2020, incremental shares of common stock that were excluded from the calculation of diluted earnings per share because these would have been antidilutive due to the Company’s net loss position were 1,853,427 shares, which also includes shares that are considered participating securities as described in (1) above. For the three and nine months ended June 30, 2019, 983,081 and 945,246 incremental shares of common stock, respectively, were excluded from the calculation of diluted earnings per share because the inclusion of these shares would have been antidilutive.

Restructuring

9 Months Ended

Jun. 30, 2020

Restructuring And Related Activities [Abstract]

Restructuring

K. Restructuring

Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations in the three and nine months ended June 30, 2020 and 2019 as follows:

	Three Months Ended June 30				Nine Months Ended June 30
	2020		2019		2020		2019
	(In millions)
Cost of sales	$	—	$	2	$	5	$	7
Selling and administrative expenses		3		2		11		8
Total	$	3	$	4	$	16	$	15

Details of all restructuring activities and the related reserves during the three and nine months ended June 30, 2020 were as follows:

	Severance and Employee Benefits			Environmental Remediation		Accelerated Depreciation and Idle Asset Depreciation			Other			Total
	(In millions)
Reserve at September 30, 2019	$	3		$	4	$	—		$	—		$	7
Charges (gain)		7			—		—			1			8
Cash paid		(2	)		—		—			(1	)		(3	)
Reserve at December 31, 2019		8			4		—			—			12
Charges (gain)		3			—		1			1			5
Costs charged against assets / (liabilities)		—			—		(1	)		—			(1	)
Cash paid		(5	)		—		—			(1	)		(6	)
Reserve at March 31, 2020		6			4		—			—			10
Charges (gain)		1			—		—			2			3
Cash paid		(2	)		—		—			(2	)		(4	)
Reserve at June 30, 2020	$	5		$	4	$	—		$	—		$	9

Cabot’s severance and employee benefit reserves and other closure related reserves are reflected in Accounts payable and accrued liabilities on the Company’s Consolidated Balance Sheets. Cabot’s environmental remediation reserves related to restructuring activities are reflected in Other liabilities on the Company’s Consolidated Balance Sheets.

2020 Reorganization

During the first nine months of fiscal 2020, the Company initiated several actions that it believes will enable the Company to perform certain activities more cost-effectively. These actions primarily consist of the reorganization of Cabot’s leadership structure, the creation of a Global Business Services function and other operational efficiency initiatives. As part of the creation of the Global Business Services function, certain business service activities performed at Cabot’s North American business service center are being consolidated into the Company’s European business service center. During the three and nine months ended June 30, 2020, the Company recorded charges of $3 million and $15 million, respectively, for these actions, primarily related to severance costs. The Company expects to record additional restructuring charges, primarily related to site demolition and clearing costs associated with the Company’s other operational efficiency initiatives, of approximately $1 million in fiscal 2020 and $5 million thereafter. Cabot paid approximately $3 million and $10 million related to these activities in the three and nine months ended June 30, 2020, respectively, and expects to pay approximately $3 million in the remainder of fiscal 2020 and $7 million thereafter. As of June 30, 2020, Cabot had $5 million of accrued severance charges in the Consolidated Balance Sheets related to these actions.

Purification Solutions Transformation Plan

In December 2018, the Company initiated a transformation plan to improve the long-term performance of the Purification Solutions segment. The purpose of the plan is to focus the business’s product portfolio, optimize its manufacturing assets, and streamline its organizational structure to support the new focus. The Company expects to record total charges of $10 million related to this plan, of which approximately $9 million was recorded in fiscal 2019, comprised of severance, employee benefits and professional service fees. The Company recorded nominal charges in the three months ended June 30, 2020 and $1 million of charges in the nine months ended June 30, 2020. The Company recorded charges of less than $1 million and $9 million in the three and nine months ended June 30, 2019, respectively. The Company expects to record nominal charges in the future related to this plan. Cabot paid approximately $9 million related to these activities through June 30, 2020, $8 million of which was paid in fiscal 2019, and expects to pay $1 million in the remainder of fiscal 2020. As of June 30, 2020, Cabot had less than $1 million of accrued severance and other employee benefit charges in the Consolidated Balance Sheets related to these actions.

Financial Instruments and Fair Value Measurements

9 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

L. Financial Instruments and Fair Value Measurements

The FASB authoritative guidance on fair value measurements defines fair value, provides a framework for measuring fair value, and requires certain disclosures about fair value measurements. The required disclosures focus on the inputs used to measure fair value. The guidance establishes the following hierarchy for categorizing these inputs:

Level 1	—	Quoted market prices in active markets for identical assets or liabilities

Level 2	—	Significant other observable inputs (e.g., quoted prices for similar items in active markets, quoted prices for identical or similar items in markets that are not active, inputs other than quoted prices that are observable such as interest rate and yield curves, and market-corroborated inputs)

Level 3	—	Significant unobservable inputs

There were no transfers of financial assets or liabilities measured at fair value between Level 1 and Level 2 and there were no Level 3 investments during the first nine months of either fiscal 2020 or 2019.

At June 30, 2020 and September 30, 2019, Cabot had derivatives relating to foreign currency risks, including a net investment hedge and forward foreign currency contracts, carried at fair value. At June 30, 2020, the fair value of these derivatives was a net asset of $10 million and was included in Prepaid expenses and other current assets, Accounts payable and accrued liabilities, and Other assets on the Consolidated Balance Sheets. At September 30, 2019, the fair value of these derivatives was a net asset of $1 million and was included in Prepaid expenses and other current assets and Other assets on the Consolidated Balance Sheets. These derivatives are classified as Level 2 instruments within the fair value hierarchy as the fair value determination was based on observable inputs.

At June 30, 2020 and September 30, 2019, the fair value of guaranteed investment contracts, included in Other assets on the Consolidated Balance Sheets, was $11 million and $10 million, respectively. Guaranteed investment contracts were classified as Level 2 instruments within the fair value hierarchy as the fair value determination was based on other observable inputs.

At June 30, 2020 and September 30, 2019, the fair values of cash and cash equivalents, accounts and notes receivable, accounts payable and accrued liabilities, and short-term borrowings and variable rate debt approximated their carrying values due to the short-term nature of these instruments. The carrying value and fair value of the long-term fixed rate debt were $1.15 billion and $1.27 billion, respectively, as of June 30, 2020, and $1.03 billion and $1.10 billion, respectively, as of September 30, 2019. The fair values of Cabot’s fixed rate long-term debt are estimated based on comparable quoted market prices at the respective period ends. The carrying amounts of Cabot’s floating rate long-term debt and finance and operating lease obligations approximate their fair values. All such measurements are based on observable inputs and are classified as Level 2 within the fair value hierarchy. The valuation technique used is the discounted cash flow model.

Derivatives

9 Months Ended

Jun. 30, 2020

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Derivatives

M. Derivatives

Foreign Currency Risk Management

Cabot’s international operations are subject to certain risks, including currency exchange rate fluctuations and government actions. Cabot endeavors to match the currency in which debt is issued to the currency of the Company’s major, stable cash receipts. In some situations, Cabot has issued debt denominated in U.S. dollars and then entered into cross-currency swaps that exchange the dollar principal and interest payments into Euro-denominated principal and interest payments.

Additionally, the Company has foreign currency exposure arising from its net investments in foreign operations. Cabot may enter into cross-currency swaps to mitigate the impact of currency rate changes on the Company’s net investments.

The Company also has foreign currency exposure arising from the denomination of monetary assets and liabilities in foreign currencies other than the functional currency of a given subsidiary as well as the risk that currency fluctuations could affect the dollar value of future cash flows generated in foreign currencies. Accordingly, Cabot uses short-term forward contracts to minimize the exposure to foreign currency risk. In certain situations where the Company has forecasted purchases under a long-term commitment or forecasted sales denominated in a foreign currency, Cabot may enter into appropriate financial instruments in accordance with the Company’s risk management policy to hedge future cash flow exposures.

The following table provides details of the derivatives held as of June 30, 2020 and September 30, 2019 to manage foreign currency risk.

		Notional Amount
Description	Borrowing	June 30, 2020	September 30, 2019	Hedge Designation
Cross-Currency Swaps	3.4% Notes	USD 250 million swapped to EUR 223 million	USD 250 million swapped to EUR 223 million	Net investment
Forward Foreign Currency Contracts ⁽¹⁾	N/A	USD 32 million	USD 54 million	No designation

⁽¹⁾	Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna.

Accounting for Derivative Instruments and Hedging Activities

The Company has cross-currency swaps with a notional amount of $250 million, which are designated as hedges of its net investments in certain Euro-denominated subsidiaries. Cash settlements occur semi-annually on March 15^th and September 15^th for fixed rate interest payments and a cash exchange of the notional currency amount will occur at the end of the term in 2026. As of June 30, 2020, the fair value of these swaps was a net asset of $10 million and was included in Prepaid expenses and other current assets and Other assets and the cumulative gain of $13 million was included in AOCI on the Consolidated Balance Sheets. As of September 30, 2019, the fair value of these swaps was a net asset of $1 million and was included in Prepaid expenses and other current assets and Other assets and the cumulative gain of $5 million was included in AOCI on the Consolidated Balance Sheets.

The following table summarizes the impact of the cross-currency swaps to AOCI and the Consolidated Statements of Operations:

	Three Months Ended June 30
	2020		2019			2020			2019			2020		2019
Description	Gain/(Loss) Recognized in AOCI					(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations						(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)
	(In millions)
Cross-currency swaps	$	1	$	(1	)	$	(2	)	$	(1	)	$	—	$	—

	Nine Months Ended June 30
	2020		2019		2020			2019			2020		2019
Description	Gain/(Loss) Recognized in AOCI				(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations						(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)
	(In millions)
Cross-currency swaps	$	11	$	12	$	(4	)	$	(4	)	$	1	$	1

Other Derivative Instruments

From time to time, the Company may enter into certain derivative instruments that may not be designated as hedges for accounting purposes, which may include cross-currency swaps, foreign currency forward contracts and commodity derivatives. For cross-currency swaps and foreign currency forward contracts not designated as hedges, the Company uses standard models with market-based inputs. The significant inputs to these models are interest rate curves for discounting future cash flows, and exchange rate curves of the foreign currency for translating future cash flows. In determining the fair value of the commodity derivatives, the significant inputs to valuation models are quoted market prices of similar instruments in active markets. Although these derivatives do not qualify for hedge accounting, Cabot believes that such instruments are closely correlated with the underlying exposure, thus managing the associated risk. The gains or losses from changes in the fair value of derivative instruments that are not accounted for as hedges are recognized in current period earnings.

At both June 30, 2020 and September 30, 2019, the fair value of derivative instruments not designated as hedges were nominal, and these instruments were presented in Prepaid expenses and other current assets and Accounts payable and accrued liabilities on the Consolidated Balance Sheets.

Financial Information by Segment

9 Months Ended

Jun. 30, 2020

Segment Reporting [Abstract]

Financial Information by Segment

N. Financial Information by Segment

The Company identifies a business as an operating segment if: (i) it engages in business activities from which it may earn revenues and incur expenses; (ii) its operating results are regularly reviewed by the Chief Operating Decision Maker (“CODM”), who is Cabot’s President and Chief Executive Officer, to make decisions about resources to be allocated to the segment and assess its performance; and (iii) it has available discrete financial information. The Company has determined that all of its businesses are operating segments. The CODM reviews financial information at the operating segment level to allocate resources and to assess the operating results and financial performance for each operating segment. Operating segments are aggregated into a reportable segment if the operating segments are determined to have similar economic characteristics and if the operating segments are similar in the following areas: (i) nature of products and services; (ii) nature of production processes; (iii) type or class of customer for their products and services; (iv) methods used to distribute the products or provide services; and (v) if applicable, the nature of the regulatory environment.

The Company has three reportable segments: Reinforcement Materials, Performance Chemicals and Purification Solutions. The Company’s former Specialty Fluids business was a separate reporting segment prior to divestiture in the third quarter of fiscal 2019.

The Reinforcement Materials segment consists of the rubber blacks and elastomer composites product lines.

The Performance Chemicals segment combines the specialty carbons, fumed metal oxides and aerogel product lines into the Performance Additives business, and combines the specialty compounds and inkjet colorants product lines into the Formulated Solutions business. These businesses are similar in terms of economic characteristics, nature of products, processes, customer class and product distribution methods, and, therefore, have been aggregated into one reportable segment. The net sales from each of these businesses for the three and nine months ended June 30, 2020 and 2019 were as follows:

	Three Months Ended June 30				Nine Months Ended June 30
	2020		2019		2020		2019
	(In millions)
Performance Additives	$	151	$	172	$	489	$	518
Formulated Solutions		69		79		218		218
Total Performance Chemicals	$	220	$	251	$	707	$	736

The Purification Solutions segment consists of the Company’s activated carbon business.

Income (loss) before income taxes (“Segment EBIT”) is presented for each reportable segment in the table below. Segment EBIT excludes Interest expense, general unallocated income (expense), unallocated corporate costs, and certain items, meaning items management does not consider representative of on-going operating segment results. In addition, Segment EBIT includes Equity in earnings of affiliated companies, net of tax, the full operating results of a contractual joint venture in Purification Solutions, royalties, Net income attributable to noncontrolling interests, net of tax, and discounting charges for certain Notes receivable.

Financial information by reportable segment is as follows:

	Reinforcement Materials			Performance Chemicals		Purification Solutions			Specialty Fluids⁽¹⁾		Segment Total		Unallocated and Other⁽²⁾			Consolidated Total
	(In millions)
Three Months Ended June 30, 2020
Revenues from external customers⁽³⁾	$	197		$	220	$	63		$	—	$	480	$	38		$	518
Income (loss) before income taxes⁽⁴⁾	$	(5	)	$	21	$	2		$	—	$	18	$	(29	)	$	(11	)

Three Months Ended June 30, 2019
Revenues from external customers⁽³⁾	$	461		$	251	$	73		$	13	$	798	$	47		$	845
Income (loss) before income taxes⁽⁴⁾	$	72		$	37	$	1		$	2	$	112	$	(43	)	$	69

Nine Months Ended June 30, 2020
Revenues from external customers⁽³⁾	$	931		$	707	$	186		$	—	$	1,824	$	131		$	1,955
Income (loss) before income taxes⁽⁴⁾	$	103		$	93	$	3		$	—	$	199	$	(148	)	$	51

Nine Months Ended June 30, 2019
Revenues from external customers⁽³⁾	$	1,363		$	736	$	210		$	56	$	2,365	$	145		$	2,510
Income (loss) before income taxes⁽⁴⁾	$	195		$	111	$	(1	)	$	24	$	329	$	(141	)	$	188

⁽¹⁾

^{Cabot divested its Specialty Fluids business during the third quarter of fiscal 2019. The agreement to divest this business did not meet the criteria for reporting this business as a discontinued operation, and therefore, the prior period’s financial statements and disclosures have not been recast. For more detail on the sale of the Specialty Fluids business, please refer to the 2019 10-K and Note C above.}

⁽²⁾	^{Unallocated and Other includes certain items and eliminations necessary to reflect management’s reporting of operating segment results. These items are reflective of the segment reporting presented to the CODM.}

⁽³⁾

Consolidated Total Revenues from external customers reconciles to Net sales and other operating revenues on the Consolidated Statements of Operations. Revenues from external customers that are categorized as Unallocated and Other reflects royalties, external shipping and handling fees, the impact of unearned revenue, the removal of 100% of the sales of an equity method affiliate, discounting charges for certain Notes receivable, and by-product revenue. Details are provided in the table below:

	Three Months Ended June 30					Nine Months Ended June 30
	2020		2019			2020		2019
	(In millions)
Royalties, the impact of unearned revenue, the removal of 100% of the sales of an equity method affiliate and discounting charges for certain notes receivable	$	4	$	(3	)	$	2	$	(9	)
Shipping and handling fees		22		32			83		96
By-product sales		12		18			46		58
Total	$	38	$	47		$	131	$	145

⁽⁴⁾	Consolidated Total Income (loss) before income taxes reconciles to Income (loss) before income taxes and equity in earnings of affiliated companies on the Consolidated Statements of Operations. Income (loss) before income taxes that are categorized as Unallocated and Other includes:

	Three Months Ended June 30						Nine Months Ended June 30
	2020			2019			2020			2019
	(In millions)
Interest expense	$	(13	)	$	(14	)	$	(41	)	$	(43	)
Certain items^(a)
Legal and environmental matters and reserves		(1	)		—			(51	)		(1	)
Global restructuring activities (Note K)		(3	)		(4	)		(16	)		(15	)
Employee benefit plan settlements		(2	)		—			(5	)		3
Acquisition and integration-related charges		(1	)		(1	)		(3	)		(5	)
Indirect tax settlement credits		—			—			3			—
Specialty Fluids loss on sale and asset impairment charge (Note C)		—			(8	)		(1	)		(28	)
Equity affiliate investment impairment charge		—			—			—			(11	)
Other		—			(1	)		(1	)		(4	)
Total certain items, pre-tax		(7	)		(14	)		(74	)		(61	)
Unallocated corporate costs^(b)		(10	)		(14	)		(32	)		(39	)
General unallocated income (expense)^(c)		2			—			1			3
Less: Equity in earnings of affiliated companies, net of tax^(d)		1			1			2			1
Total	$	(29	)	$	(43	)	$	(148	)	$	(141	)

^(a)

Certain items are items of expense and income that management does not consider representative of the Company’s fundamental on-going segment results and they are, therefore, excluded from Segment EBIT.

^(b)

Unallocated corporate costs are costs that are not controlled by the segments and primarily benefit corporate interests.

^(c)

General unallocated income (expense) consists of gains (losses) arising from foreign currency transactions, net of other foreign currency risk management activities, Interest and dividend income, the profit or loss related to the corporate adjustment for unearned revenue, the impact of including the full operating results of a contractual joint venture in Purification Solutions Segment EBIT and unrealized holding gains (losses) for equity securities.

^(d)

Equity in earnings of affiliated companies, net of tax, is included in Segment EBIT and is removed in Unallocated and other to reconcile to Income (loss) from operations before income taxes and equity in earnings from affiliated companies.

The Company’s segments operate globally. In addition to presenting Revenue from external customers by reportable segment, the following tables further disaggregate Revenues from external customers by geographic region.

	Three Months Ended June 30, 2020
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Consolidated Total
	(In millions)
Americas	$	59	$	54	$	28	$	141
Asia Pacific		106		98		8		212
Europe, Middle East and Africa		32		68		27		127
Segment revenues from external customers		197		220		63		480
Unallocated and other								38
Net sales and other operating revenues							$	518

	Three Months Ended June 30, 2019
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Specialty Fluids		Consolidated Total
	(In millions)
Americas	$	179	$	69	$	33	$	2	$	283
Asia Pacific		191		93		10		—		294
Europe, Middle East and Africa		91		89		30		11		221
Segment revenues from external customers		461		251		73		13		798
Unallocated and other										47
Net sales and other operating revenues									$	845

	Nine Months Ended June 30, 2020
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Consolidated Total
	(In millions)
Americas	$	354	$	206	$	83	$	643
Asia Pacific		398		271		26		695
Europe, Middle East and Africa		179		230		77		486
Segment revenues from external customers		931		707		186		1,824
Unallocated and other								131
Net sales and other operating revenues							$	1,955

	Nine Months Ended June 30, 2019
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Specialty Fluids		Consolidated Total
	(In millions)
Americas	$	515	$	222	$	93	$	6	$	836
Asia Pacific		573		253		26		1		853
Europe, Middle East and Africa		275		261		91		49		676
Segment revenues from external customers		1,363		736		210		56		2,365
Unallocated and other										145
Net sales and other operating revenues									$	2,510

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2020
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition Cabot recognizes revenue when its customers obtain control of promised goods or services. The revenue recognized is the amount of consideration that the Company expects to receive in exchange for those goods or services. The Company’s contracts with customers are generally for products only and do not include other performance obligations. Generally, Cabot considers purchase orders, which in some cases are governed by master supply agreements, to be contracts with customers. The transaction price as specified on the purchase order or sales contract is considered the standalone selling price for each distinct product. To determine the transaction price at the time when revenue is recognized, the Company evaluates whether the price is subject to adjustments, such as for returns, discounts or volume rebates, which are stated in the customer contract, to determine the net consideration to which the Company expects to be entitled. Revenue from product sales is recognized based on a point in time model when control of the product is transferred to the customer, which typically occurs upon shipment or delivery of the product to the customer and title, risk and rewards of ownership have passed to the customer. The Company has an immaterial amount of revenue that is recognized over time. Payment terms typically range from zero to ninety days. Shipping and handling costs incurred after the transfer of control of a product to the customer are billed to the customer and are recorded as sales revenue, as the Company considers these to be fulfillment costs. Shipping and handling costs are expensed in the period incurred and included in Cost of sales within the Consolidated Statement of Operations. Taxes collected on sales to customers are excluded from the transaction price. The Company generally provides a warranty that its products will substantially conform to the identified specifications. The Company’s liability typically is limited to either a credit equal to the purchase price or replacement of the non-conforming product. Returns under warranty have historically been immaterial. The Company does not have contract assets or liabilities that are material. As permitted by the FASB’s revenue recognition standard, Revenue from Contracts with Customers, when the period of time between the transfer of control of the goods and the time the customer pays for the goods is one year or less, the Company does not consider there to be a significant financing component associated with the contract.
Intangible Assets and Goodwill Impairment	Intangible Assets and Goodwill Impairment The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for assets acquired and liabilities assumed in an acquisition are allocated to the assets and liabilities based on their fair values at the date of acquisition. The Company uses assumptions and estimates in determining the fair value of assets acquired and liabilities assumed in a business combination. The determination of the fair value of intangible assets requires the use of significant judgment with regard to assumptions used in the valuation model. The Company estimates the fair value of identifiable acquisition-related intangible assets principally based on projections of cash flows that will arise from these assets. The projected cash flows are discounted to determine the fair value of the assets at the dates of acquisition. Definite-lived intangible assets, which are comprised of trademarks, customer relationships and developed technologies, are amortized over their estimated useful lives and are reviewed for impairment when indication of potential impairment exists, such as a significant reduction in cash flows associated with the assets. Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value assigned to the net tangible and identifiable intangible assets acquired. Goodwill is not amortized, but is reviewed for impairment annually as of August 31, or when events or changes in the business environment indicate that the carrying value of the reporting unit may exceed its fair value. A reporting unit, for the purpose of the impairment test, is at or below the operating segment level, and constitutes a business for which discrete financial information is available and regularly reviewed by segment management. Reinforcement Materials, and the fumed metal oxides, specialty compounds and specialty carbons product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of June 30, 2020. For the purpose of the goodwill impairment test, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value, an additional quantitative evaluation is performed. Alternatively, the Company may elect to proceed directly to the quantitative goodwill impairment test. If based on the quantitative evaluation the fair value of the reporting unit is less than its carrying amount, a goodwill impairment loss would result. The goodwill impairment loss would be the amount by which the carrying value of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. The fair value of a reporting unit is based on discounted estimated future cash flows. The fair value is also benchmarked against a market approach using the guideline public company method. The assumptions used to estimate fair value include management’s best estimates of future growth rates, operating cash flows, capital expenditures and discount rates over an estimate of the remaining operating period at the reporting unit level. Based on the Company’s most recent annual goodwill impairment test performed as of August 31, 2019, the fair values of the Reinforcement Materials, Fumed Metal Oxides and Specialty Compounds reporting units were substantially in excess of their carrying values.
Long-Lived Assets Impairment	Long-lived Assets Impairment The Company’s long-lived assets primarily include property, plant and equipment, intangible assets and long-term investments. The carrying values of long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. To test for impairment of assets, the Company generally uses a probability-weighted estimate of the future undiscounted net cash flows of the assets over their remaining lives to determine if the value of the asset is recoverable. Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable. An asset impairment is recognized when the carrying value of the asset is not recoverable based on the analysis described above, in which case the asset is written down to its fair value. If the asset does not have a readily determinable fair value, a discounted cash flow model may be used to determine the fair value of the asset. In circumstances when an asset does not have separately identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset. The Company continues to consider strategic options for its Purification Solutions business. Depending on the actions taken, there could be a negative impact on the fair value of the Purification Solutions reporting unit, which may lead to an impairment.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The depreciable lives for buildings, machinery and equipment, and other fixed assets are between twenty and twenty-five years, ten and twenty-five years, and three and twenty-five years, respectively. The cost and accumulated depreciation for property, plant and equipment sold, retired, or otherwise disposed of are removed from the Consolidated Balance Sheets and resulting gains or losses are included in earnings in the Consolidated Statements of Operations. Expenditures for repairs and maintenance are charged to expenses as incurred. Expenditures for major renewals and betterments, which significantly extend the useful lives of existing plant and equipment, are capitalized and depreciated.
Income Tax in Interim Periods	Income Tax in Interim Periods The Company records its tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period. Valuation allowances are provided against the future tax benefits that arise from the deferred tax assets in jurisdictions for which no benefit can be recognized. The estimated annual effective tax rate may be significantly impacted by nondeductible expenses and the Company’s projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised.
Inventory Valuation	Inventory Valuation Inventories are stated at the lower of cost or net realizable value. The cost of inventory is determined using the FIFO method. Cabot periodically reviews inventory for both potential obsolescence and potential declines in anticipated selling prices. In this review, the Company makes assumptions about the future demand for and market value of the inventory, and based on these assumptions estimates the amount of any obsolete, unmarketable, slow moving, or overvalued inventory. Cabot writes down the value of these inventories by an amount equal to the difference between the cost of the inventory and its estimated net realizable value.
Pensions and Other Postretirement Benefits	Pensions and Other Postretirement Benefits The Company recognizes the funded status of defined benefit pension and other postretirement benefit plans as an asset or liability. This amount is defined as the difference between the fair value of plan assets and the benefit obligation. Pension and post-retirement benefit costs other than service cost are included in Other income (expense) in the Consolidated Statement of Operations. The Company is required to recognize as a component of Other comprehensive income (loss), net of tax, the actuarial gains/losses and prior service costs/credits that arise but were not previously required to be recognized as components of net periodic benefit cost. Other comprehensive income (loss) is adjusted as these amounts are later recognized in income as components of net periodic benefit cost.
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Accumulated other comprehensive income (loss) (“AOCI”), which is included as a component of stockholders’ equity, includes unrealized gains or losses on derivative instruments, currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In February 2016, the FASB issued a new standard for the accounting for leases. This standard requires lessees to recognize assets and liabilities for most leases, but recognize expenses on their income statements in a manner that is similar to the historical accounting treatment for leases. The Company adopted the standard on October 1, 2019 using the modified retrospective optional transition method. Accordingly, leases in the prior period continue to be reported and disclosed in accordance with the Company’s historical accounting treatment. The Company elected the package of practical expedients that permits the Company to not reassess the identification, classification and initial direct costs of leases commencing before the October 1, 2019 effective date and to exclude short-term leases from the balance sheet. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases or the practical expedient to not separate lease and non-lease components to existing leases, as well as new leases, through transition. The Company allocates the total consideration to the lease components and non-lease components on an observable stand-alone price basis to all asset classes. Adoption of the new lease standard resulted in the recognition of operating lease right-of-use (“ROU”) assets and operating lease liabilities of approximately $106 million and $111 million, respectively, as of October 1, 2019. Refer to Note H for further details regarding the balance sheet classification of these items. The difference between the operating lease ROU assets and operating lease liabilities reflects the reclassification of historical deferred rent balances of approximately $5 million. The effects of transition to the new standard resulted in no cumulative adjustment to retained earnings in the period of adoption. The standard did not materially impact the Company’s Consolidated Statement of Operations or Consolidated Statement of Cash Flows. The new standard did not have a material impact on the Company’s liquidity or debt-covenant compliance as of adoption. In February 2018, the FASB issued a new standard that allows entities to reclassify from Accumulated other comprehensive income (loss) (“AOCI”) to Retained earnings stranded tax effects resulting from changes made as a result of the Tax Cuts and Jobs Act of 2017 (the “Act”). The Company adopted this standard on October 1, 2019 which resulted in the reclassification of a $2 million net gain from AOCI to Retained earnings. The reclassification was primarily related to the Company’s pension plans and derivative instruments.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued a new standard on measurement of credit losses. The standard introduces an "expected loss" impairment model that applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables and other financial assets. Entities are required to estimate expected credit losses over the life of financial assets and record an allowance against the assets’ amortized cost basis to present them at the amount expected to be collected. The new standard is effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The Company will adopt this standard effective October 1, 2020. The Company does not expect the adoption of this standard to materially impact the Company’s consolidated financial statements. In March 2020, the FASB issued a new standard on Reference Rate Reform, which provides temporary optional expedients and exceptions to the existing guidance on contract modifications and hedge accounting to ease the financial reporting burdens related to the expected market transition from the London Interbank Offered Rate ("LIBOR") and other interbank offered rates to alternative reference rates. The standard was effective upon issuance and may generally be applied through December 31, 2022 to any new or amended contracts, hedging relationships, and other transactions that reference LIBOR. The Company is currently evaluating the timing of adoption and the impact of the adoption of this standard on its consolidated financial statements.

Acquisitions and Divestitures (Tables)

9 Months Ended

Jun. 30, 2020

Business Combinations [Abstract]

Schedule of Allocation of Purchase Price Based on Estimates of Fair Value of Assets Acquired and Liabilities Assumed

The provisional allocation of the purchase price set forth below was based on estimates of the fair value of assets acquired and liabilities assumed as of April 1, 2020.

	(In millions)
Assets
Cash	$	1
Accounts Receivable		8
Inventories		4
Prepaid expenses and other current assets		2
Property, plant and equipment		38
Intangible assets		15
Goodwill		45
Deferred tax asset		1
Other assets		2
Total assets acquired		116

Liabilities
Accounts payable and accrued liabilities		(12	)
Income taxes payable		(2	)
Long-term debt		(13	)
Other liabilities		(4	)

Total liabilities assumed		(31	)

Cash consideration paid	$	85

Employee Benefit Plans (Tables)

9 Months Ended

Jun. 30, 2020

Compensation And Retirement Disclosure [Abstract]

Net Periodic Defined Benefit Pension Costs

Net periodic defined benefit pension costs include the following:

	Three Months Ended June 30
	2020						2019
	Pension Benefits
	U.S.			Foreign			U.S.			Foreign
	(In millions)
Service cost	$	—		$	1		$	1		$	2
Interest cost		1			1			1			1
Expected return on plan assets		(1	)		(2	)		(2	)		(2	)
Amortization of prior service costs (credit)		—			—			—			2
Amortization of actual loss		—			1			—			1
Net periodic benefit (credit) cost	$	—		$	1		$	—		$	4

	Nine Months Ended June 30
	2020						2019
	Pension Benefits
	U.S.			Foreign			U.S.			Foreign
	(In millions)
Service cost	$	1		$	4		$	1		$	5
Interest cost		3			3			4			4
Expected return on plan assets		(3	)		(7	)		(7	)		(8	)
Amortization of prior service cost (credit)		—			—			—			2
Amortization of actuarial loss		—			2			—			2
Settlement and curtailment gain		—			—			—			(6	)
Net periodic benefit (credit) cost	$	1		$	2		$	(2	)	$	(1	)

Goodwill and Intangible Assets (Tables)

9 Months Ended

Jun. 30, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

Schedule of Goodwill Balances

The carrying amount of goodwill attributable to each reportable segment with goodwill balances and the changes in those balances during the nine month period ended June 30, 2020 are as follows:

	Reinforcement Materials			Performance Chemicals		Total
	(In millions)
Balance at September 30, 2019	$	50		$	40	$	90
Goodwill acquired⁽¹⁾		—			45		45
Foreign currency impact		(5	)		—		(5	)
Balance at June 30, 2020	$	45		$	85	$	130

⁽¹⁾Consists of goodwill acquired in the acquisition of SUSN as described in Note C.

Schedule of Intangible Assets

The following table provides information regarding the Company’s intangible assets:

	June 30, 2020							September 30, 2019
	Gross Carrying Value		Accumulated Amortization			Net Intangible Assets		Gross Carrying Value		Accumulated Amortization			Net Intangible Assets
	(In millions)
Intangible assets with finite lives
Developed technologies	$	58	$	(7	)	$	51	$	50	$	(5	)	$	45
Trademarks		11		(1	)		10		8		—			8
Customer relationships		54		(13	)		41		57		(14	)		43
Total intangible assets⁽¹⁾	$	123	$	(21	)	$	102	$	115	$	(19	)	$	96

Accumulated Other Comprehensive Income (Loss) (Tables)

9 Months Ended

Jun. 30, 2020

Equity [Abstract]

Changes in Each Component of AOCI, Net of Tax

Changes in each component of AOCI, net of tax, were as follows:

	Currency Translation Adjustment			Unrealized Gains on Investments			Pension and Other Postretirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2019, attributable to Cabot Corporation	$	(338	)	$	1		$	(54	)	$	(391	)
Other comprehensive income (loss) before reclassifications		43			—			—			43
Amounts reclassified from AOCI		(1	)		—			1			—
Adoption of accounting standards		(3	)		(1	)		1			(3	)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		3			—			—			3
Balance at December 31, 2019, attributable to Cabot Corporation		(302	)		—			(52	)		(354	)
Other comprehensive income (loss) before reclassifications		(78	)		—			—			(78	)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		(3	)		—			—			(3	)
Balance at March 31, 2020, attributable to Cabot Corporation		(377	)		—			(52	)		(429	)
Other comprehensive income (loss) before reclassifications		31			—			(1	)		30
Amounts reclassified from AOCI		(1	)		—			2			1
Less: Other comprehensive income (loss) attributable to noncontrolling interests		2			—			—			2
Balance at June 30, 2020, attributable to Cabot Corporation	$	(349	)	$	—		$	(51	)	$	(400	)

Amounts Reclassified Out of AOCI

The amounts reclassified out of AOCI and into the Consolidated Statements of Operations in the three and nine months ended June 30, 2020 and 2019 were as follows:

	Affected Line Item in the Consolidated	Three Months Ended June 30						Nine Months Ended June 30
	Statements of Operations	2020			2019			2020			2019
		(In millions)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense	Interest expense	$	(2	)	$	(1	)	$	(4	)	$	(4	)
(Gains) losses excluded from effectiveness testing and amortized to interest expense	Interest expense		—			—			1			1
Pension and other postretirement
Amortization of actuarial losses and prior service cost (credit)	Net Periodic Benefit Cost - see Note D for details		2			2			3			2
Settlement and curtailment gain	Net Periodic Benefit Cost - see Note D for details		—			—			—			(6	)
Total before tax			—			1			—			(7	)
Tax impact	Provision (benefit) for income taxes		1			1			1			(2	)
Total after tax		$	1		$	2		$	1		$	(9	)

Leases (Tables)

9 Months Ended

Jun. 30, 2020

Leases [Abstract]

Components of Company's Lease Costs

The components of the Company’s lease costs were as follows:

	Three Months Ended June 30		Nine Months Ended June 30
	2020		2020
	(In millions)
Operating lease cost	$	7	$	24
Finance lease cost		2		4
Total lease cost	$	9	$	28

Supplemental Cash Flow Information Related to Company's Leases

Supplemental cash flow information related to the Company’s leases was as follows:

	Three Months Ended June 30		Nine Months Ended June 30
	2020		2020
	(In millions)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	7	$	19
Operating cash flows from finance leases		—		1
Financing cash flows from finance leases		1		2
Right-of-use assets obtained in exchange for new operating lease liabilities	$	8	$	13
Right-of-use assets obtained in exchange for new finance lease liabilities	$	—	$	23

Supplemental Balance Sheet Information Related to Company's Leases

Supplemental balance sheet information related to the Company’s leases was as follows:

Description	Balance Sheet Classification	June 30, 2020
		(In millions)
Lease ROU assets:
Operating	Other assets	$	102
Finance	Net property, plant and equipment		45
Total lease ROU assets		$	147

Lease liabilities:
Current:
Operating	Accounts payable and accrued liabilities	$	17
Finance	Current portion of long-term debt		3
Long-term:
Operating	Other liabilities		91
Finance	Long-term debt		28
Total lease liabilities		$	139

Weighed Average Remaining Lease Term and Discount Rates

The following table presents the weighted-average remaining lease term and discount rates for the Company’s leases as of June 30, 2020:

Description	June 30, 2020
Weighted-average remaining lease term (years):
Operating leases		16
Finance leases		12
Weighted-average discount rate:
Operating leases		2.21	%
Finance leases		4.44	%

Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases

Future minimum lease payments under non-cancelable operating and finance leases as of June 30, 2020 were as follows:

Years Ended September 30	Operating leases		Finance leases
	(In millions)
Remainder of fiscal 2020	$	6	$	1
2021		16		5
2022		12		4
2023		10		4
2024		10		4
2025 and thereafter		75		25
Total lease payments		129		43
Less: imputed interest		21		12
Total	$	108	$	31

The Company’s future minimum lease payments under noncancelable leases as of September 30, 2019 were as follows:

Years Ended September 30	Operating leases		Capital leases
	(In millions)
2020	$	23	$	3
2021		14		3
2022		9		3
2023		9		3
2024		8		2
2025 and thereafter		68		7
Total lease payments		131		21
Less: imputed interest		—		9
Total	$	131	$	12

Income Tax (Tables)

9 Months Ended

Jun. 30, 2020

Income Tax Disclosure [Abstract]

Effective Tax Rate

	Three Months Ended June 30						Nine Months Ended June 30
	2020			2019			2020			2019
	(Dollars in millions)
(Provision) benefit for income taxes	$	5		$	(30	)	$	(9	)	$	(43	)
Effective tax rate		51	%		43	%		17	%		23	%

Earnings Per Share (Tables)

9 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS)

The following tables summarize the components of the basic and diluted earnings (loss) per common share (“EPS”) computations:

	Three Months Ended June 30					Nine Months Ended June 30
	2020			2019		2020		2019
	(In millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to Cabot Corporation	$	(6	)	$	32	$	34	$	124
Less: Dividends and dividend equivalents to participating securities		—			—		—		—
Earnings (loss) allocated to common shareholders (numerator)	$	(6	)	$	32	$	34	$	124

Weighted average common shares and participating securities outstanding		57.2			59.0		57.4		59.9
Less: Participating securities⁽¹⁾		0.7			0.8		0.7		0.8
Adjusted weighted average common shares (denominator)		56.5			58.2		56.7		59.1

Earnings (loss) per common share - basic:	$	(0.12	)	$	0.55	$	0.59	$	2.08

Diluted EPS:
Earnings (loss) allocated to common shareholders	$	(6	)	$	32	$	34	$	124
Plus: Earnings allocated to participating securities		—			—		—		1
Less: Adjusted earnings allocated to participating securities⁽²⁾		—			—		—		1
Earnings (loss) allocated to common shareholders (numerator)	$	(6	)	$	32	$	34	$	124

Adjusted weighted average common shares outstanding		56.5			58.2		56.7		59.1
Effect of dilutive securities:
Common shares issuable⁽³⁾		—			0.2		—		0.1
Adjusted weighted average common shares (denominator)		56.5			58.4		56.7		59.2

Earnings (loss) per common share - diluted:	$	(0.12	)	$	0.55	$	0.59	$	2.08

⁽¹⁾

Calculation of Undistributed Earnings

	Three Months Ended June 30					Nine Months Ended June 30
	2020			2019		2020			2019
	(In millions)
Calculation of undistributed earnings (loss):
Net income (loss) attributable to Cabot Corporation	$	(6	)	$	32	$	34		$	124
Less: Dividends declared on common stock		20			20		60			60
Less: Dividends declared on participating securities		—			—		—			—
Undistributed earnings (loss)	$	(26	)	$	12	$	(26	)	$	64

Allocation of undistributed earnings (loss):
Undistributed earnings (loss) allocated to common shareholders	$	(26	)	$	12	$	(26	)	$	64
Undistributed earnings allocated to participating shareholders		—			—		—			—
Undistributed earnings (loss)	$	(26	)	$	12	$	(26	)	$	64

⁽²⁾	Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (3) below, and then reallocated to participating securities.

⁽³⁾

Restructuring (Tables)

9 Months Ended

Jun. 30, 2020

Restructuring And Related Activities [Abstract]

Recorded Restructuring Activities

Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations in the three and nine months ended June 30, 2020 and 2019 as follows:

	Three Months Ended June 30				Nine Months Ended June 30
	2020		2019		2020		2019
	(In millions)
Cost of sales	$	—	$	2	$	5	$	7
Selling and administrative expenses		3		2		11		8
Total	$	3	$	4	$	16	$	15

Restructuring Activities and Related Reserves

Details of all restructuring activities and the related reserves during the three and nine months ended June 30, 2020 were as follows:

	Severance and Employee Benefits			Environmental Remediation		Accelerated Depreciation and Idle Asset Depreciation			Other			Total
	(In millions)
Reserve at September 30, 2019	$	3		$	4	$	—		$	—		$	7
Charges (gain)		7			—		—			1			8
Cash paid		(2	)		—		—			(1	)		(3	)
Reserve at December 31, 2019		8			4		—			—			12
Charges (gain)		3			—		1			1			5
Costs charged against assets / (liabilities)		—			—		(1	)		—			(1	)
Cash paid		(5	)		—		—			(1	)		(6	)
Reserve at March 31, 2020		6			4		—			—			10
Charges (gain)		1			—		—			2			3
Cash paid		(2	)		—		—			(2	)		(4	)
Reserve at June 30, 2020	$	5		$	4	$	—		$	—		$	9

Derivatives (Tables)

9 Months Ended

Jun. 30, 2020

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Details of Derivatives Held to Manage Foreign Currency Risk

The following table provides details of the derivatives held as of June 30, 2020 and September 30, 2019 to manage foreign currency risk.

		Notional Amount
Description	Borrowing	June 30, 2020	September 30, 2019	Hedge Designation
Cross-Currency Swaps	3.4% Notes	USD 250 million swapped to EUR 223 million	USD 250 million swapped to EUR 223 million	Net investment
Forward Foreign Currency Contracts ⁽¹⁾	N/A	USD 32 million	USD 54 million	No designation

⁽¹⁾	Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna.

Summary Impact of Cross-currency Swaps to AOCI and Consolidated Statements of Operations

The following table summarizes the impact of the cross-currency swaps to AOCI and the Consolidated Statements of Operations:

	Three Months Ended June 30
	2020		2019			2020			2019			2020		2019
Description	Gain/(Loss) Recognized in AOCI					(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations						(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)
	(In millions)
Cross-currency swaps	$	1	$	(1	)	$	(2	)	$	(1	)	$	—	$	—

	Nine Months Ended June 30
	2020		2019		2020			2019			2020		2019
Description	Gain/(Loss) Recognized in AOCI				(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations						(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)
	(In millions)
Cross-currency swaps	$	11	$	12	$	(4	)	$	(4	)	$	1	$	1

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624163-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41620-113959

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41638-113959

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41641-113959

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579240-113959

+ Details

Financial Information by Segment (Tables)

9 Months Ended

Jun. 30, 2020

Segment Reporting [Abstract]

Schedule of Performance Segment

The net sales from each of these businesses for the three and nine months ended June 30, 2020 and 2019 were as follows:

	Three Months Ended June 30				Nine Months Ended June 30
	2020		2019		2020		2019
	(In millions)
Performance Additives	$	151	$	172	$	489	$	518
Formulated Solutions		69		79		218		218
Total Performance Chemicals	$	220	$	251	$	707	$	736

Financial Information by Reportable Segment

Financial information by reportable segment is as follows:

	Reinforcement Materials			Performance Chemicals		Purification Solutions			Specialty Fluids⁽¹⁾		Segment Total		Unallocated and Other⁽²⁾			Consolidated Total
	(In millions)
Three Months Ended June 30, 2020
Revenues from external customers⁽³⁾	$	197		$	220	$	63		$	—	$	480	$	38		$	518
Income (loss) before income taxes⁽⁴⁾	$	(5	)	$	21	$	2		$	—	$	18	$	(29	)	$	(11	)

Three Months Ended June 30, 2019
Revenues from external customers⁽³⁾	$	461		$	251	$	73		$	13	$	798	$	47		$	845
Income (loss) before income taxes⁽⁴⁾	$	72		$	37	$	1		$	2	$	112	$	(43	)	$	69

Nine Months Ended June 30, 2020
Revenues from external customers⁽³⁾	$	931		$	707	$	186		$	—	$	1,824	$	131		$	1,955
Income (loss) before income taxes⁽⁴⁾	$	103		$	93	$	3		$	—	$	199	$	(148	)	$	51

Nine Months Ended June 30, 2019
Revenues from external customers⁽³⁾	$	1,363		$	736	$	210		$	56	$	2,365	$	145		$	2,510
Income (loss) before income taxes⁽⁴⁾	$	195		$	111	$	(1	)	$	24	$	329	$	(141	)	$	188

⁽¹⁾

⁽²⁾	^{Unallocated and Other includes certain items and eliminations necessary to reflect management’s reporting of operating segment results. These items are reflective of the segment reporting presented to the CODM.}

⁽³⁾

	Three Months Ended June 30					Nine Months Ended June 30
	2020		2019			2020		2019
	(In millions)
Royalties, the impact of unearned revenue, the removal of 100% of the sales of an equity method affiliate and discounting charges for certain notes receivable	$	4	$	(3	)	$	2	$	(9	)
Shipping and handling fees		22		32			83		96
By-product sales		12		18			46		58
Total	$	38	$	47		$	131	$	145

⁽⁴⁾	Consolidated Total Income (loss) before income taxes reconciles to Income (loss) before income taxes and equity in earnings of affiliated companies on the Consolidated Statements of Operations. Income (loss) before income taxes that are categorized as Unallocated and Other includes:

	Three Months Ended June 30						Nine Months Ended June 30
	2020			2019			2020			2019
	(In millions)
Interest expense	$	(13	)	$	(14	)	$	(41	)	$	(43	)
Certain items^(a)
Legal and environmental matters and reserves		(1	)		—			(51	)		(1	)
Global restructuring activities (Note K)		(3	)		(4	)		(16	)		(15	)
Employee benefit plan settlements		(2	)		—			(5	)		3
Acquisition and integration-related charges		(1	)		(1	)		(3	)		(5	)
Indirect tax settlement credits		—			—			3			—
Specialty Fluids loss on sale and asset impairment charge (Note C)		—			(8	)		(1	)		(28	)
Equity affiliate investment impairment charge		—			—			—			(11	)
Other		—			(1	)		(1	)		(4	)
Total certain items, pre-tax		(7	)		(14	)		(74	)		(61	)
Unallocated corporate costs^(b)		(10	)		(14	)		(32	)		(39	)
General unallocated income (expense)^(c)		2			—			1			3
Less: Equity in earnings of affiliated companies, net of tax^(d)		1			1			2			1
Total	$	(29	)	$	(43	)	$	(148	)	$	(141	)

^(a)

^(b)

Unallocated corporate costs are costs that are not controlled by the segments and primarily benefit corporate interests.

^(c)

^(d)

Revenues from External Customers by Geographic Region

	Three Months Ended June 30, 2020
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Consolidated Total
	(In millions)
Americas	$	59	$	54	$	28	$	141
Asia Pacific		106		98		8		212
Europe, Middle East and Africa		32		68		27		127
Segment revenues from external customers		197		220		63		480
Unallocated and other								38
Net sales and other operating revenues							$	518

	Three Months Ended June 30, 2019
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Specialty Fluids		Consolidated Total
	(In millions)
Americas	$	179	$	69	$	33	$	2	$	283
Asia Pacific		191		93		10		—		294
Europe, Middle East and Africa		91		89		30		11		221
Segment revenues from external customers		461		251		73		13		798
Unallocated and other										47
Net sales and other operating revenues									$	845

	Nine Months Ended June 30, 2020
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Consolidated Total
	(In millions)
Americas	$	354	$	206	$	83	$	643
Asia Pacific		398		271		26		695
Europe, Middle East and Africa		179		230		77		486
Segment revenues from external customers		931		707		186		1,824
Unallocated and other								131
Net sales and other operating revenues							$	1,955

	Nine Months Ended June 30, 2019
	Reinforcement Materials		Performance Chemicals		Purification Solutions		Specialty Fluids		Consolidated Total
	(In millions)
Americas	$	515	$	222	$	93	$	6	$	836
Asia Pacific		573		253		26		1		853
Europe, Middle East and Africa		275		261		91		49		676
Segment revenues from external customers		1,363		736		210		56		2,365
Unallocated and other										145
Net sales and other operating revenues									$	2,510

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions		9 Months Ended
	Oct. 01, 2019	Jun. 30, 2020	Sep. 30, 2019
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 106	$ 102
Operating lease liability	111	108
Reclassification of deferred rent balances	5
Cumulative adjustment to retained earnings		$ 1,277	$ 1,337
Reclassification of net gain from Accumulated other comprehensive income (loss) to retained earnings	2
Cumulative Effect, Period of Adoption, Adjustment [Member] \| Revision of Prior Period, Adjustment [Member]
Significant Accounting Policies [Line Items]
Cumulative adjustment to retained earnings	$ 0
Minimum [Member]
Significant Accounting Policies [Line Items]
Payment terms		0 days
Minimum [Member] \| Buildings [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		20 years
Minimum [Member] \| Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		10 years
Minimum [Member] \| Other Fixed Assets [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Payment terms		90 days
Maximum [Member] \| Buildings [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years
Maximum [Member] \| Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years
Maximum [Member] \| Other Fixed Assets [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years

Acquisitions and Divestitures - Additional Information (Detail) - USD ($)		1 Months Ended			3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Apr. 01, 2020	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Business Acquisition [Line Items]
Businesses acquisition, net of cash acquired									$ 92,000,000	$ 3,000,000
Assumed debt repaid									334,000,000	75,000,000
Total proceeds from sale of Specialty Fluids business										130,000,000
Specialty Fluids loss on sale and asset impairment						$ 8,000,000			1,000,000	28,000,000
Specialty Fluids [Member] \| Sinomine (Hong Kong) Rare Metals Resources Co. Limited [Member]
Business Acquisition [Line Items]
Total proceeds from sale of Specialty Fluids business			$ 133,000,000
Pre-tax loss on sale of Specialty Fluids business							$ 1,000,000				$ 9,000,000
Specialty Fluids loss on sale and asset impairment								$ 20,000,000
NSCC Carbon (Jiangsu) Co. Ltd [Member]
Business Acquisition [Line Items]
Acquisition date				Sep. 30, 2018
Business acquisition, purchase price				$ 8,000,000
Expected production commencement year				2022
Transition related costs						$ 1,000,000			2,000,000	$ 4,000,000
NSCC Carbon (Jiangsu) Co. Ltd [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Transition related costs					$ 1,000,000
Shenzhen Sanshun Nano New Materials Co., Ltd [Member]
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 100,000,000
Business acquisition, cash consideration	84,000,000
Businesses acquisition, net of cash acquired	1,000,000
Business acquisition, assumed debt	13,000,000
Assumed debt repaid		$ 13,000,000
Business combination future contingent consideration milestone payment	3,000,000
Business acquisition, revenue					6,000,000
Acquisition and integration costs		$ 2,000,000			$ 2,000,000		$ 2,000,000		$ 2,000,000
Shenzhen Sanshun Nano New Materials Co., Ltd [Member] \| Developed Technologies [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 9,000,000
Intangible assets amortization period	10 years
Shenzhen Sanshun Nano New Materials Co., Ltd [Member] \| Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 4,000,000
Intangible assets amortization period	20 years
Shenzhen Sanshun Nano New Materials Co., Ltd [Member] \| Trademarks [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets	$ 2,000,000
Intangible assets amortization period	10 years

Acquisitions and Divestitures - Schedule of Allocation of Purchase Price Based on Estimates of Fair Value of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Apr. 01, 2020	Sep. 30, 2019
Assets
Cash		$ 1
Accounts Receivable		8
Inventories		4
Prepaid expenses and other current assets		2
Property, plant and equipment		38
Intangible assets		15
Goodwill	$ 130	45	$ 90
Deferred tax asset		1
Other assets		2
Total assets acquired		116
Liabilities
Accounts payable and accrued liabilities		(12)
Income taxes payable		(2)
Long-term debt		(13)
Other liabilities		(4)
Total liabilities assumed		(31)
Cash consideration paid		$ 85

Employee Benefit Plans - Net Periodic Defined Benefit Pension Costs (Detail) - Pension Benefits [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 1	$ 1	$ 1
Interest cost	$ 1	1	3	4
Expected return on plan assets	(1)	(2)	(3)	(7)
Net periodic benefit (credit) cost			1	(2)
Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2	4	5
Interest cost	1	1	3	4
Expected return on plan assets	(2)	(2)	(7)	(8)
Amortization of prior service costs (credit)		2		2
Amortization of actual / actuarial loss	1	1	2	2
Settlement and curtailment gain				(6)
Net periodic benefit (credit) cost	$ 1	$ 4	$ 2	$ (1)

Employee Benefit Plans - Additional Information (Detail)	3 Months Ended			9 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 Plan
Defined Benefit Plan Disclosure [Line Items]
Number of foreign defined benefit plans \| Plan						1
Pre-tax gain from net pension obligations			$ 6,000,000
Additional charge on defined benefit plan actuarial gain (loss)			$ 3,000,000
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan termination settlements expected future loss				$ 13,000,000
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Other postretirement benefit costs (gains)	$ 1,000,000	$ (1,000,000)		$ 1,000,000	$ (1,000,000)

Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	9 Months Ended
	Jun. 30, 2020 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 90
Goodwill acquired	45
Foreign currency impact	(5)
Ending balance	130
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	50
Foreign currency impact	(5)
Ending balance	45
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	40
Goodwill acquired	45
Ending balance	$ 85

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 123	$ 115
Accumulated Amortization	(21)	(19)
Net Intangible Assets, finite lives	102	96
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	58	50
Accumulated Amortization	(7)	(5)
Net Intangible Assets, finite lives	51	45
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	11	8
Accumulated Amortization	(1)
Net Intangible Assets, finite lives	10	8
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	54	57
Accumulated Amortization	(13)	(14)
Net Intangible Assets, finite lives	$ 41	$ 43

Goodwill and Intangible Assets - Schedule of Intangible Assets (Parenthetical) (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Apr. 01, 2020
Finite Lived Intangible Assets [Line Items]
Intangible assets		$ 15
Shenzhen Sanshun Nano New Materials Co., Ltd [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets	$ 15
Unfavorable impact of foreign currency translation	$ 4

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill And Intangible Assets [Line Items]
Amortization expense estimated for year one	$ 7		$ 7
Amortization expense estimated for year two	7		7
Amortization expense estimated for year three	7		7
Amortization expense estimated for year four	7		7
Amortization expense estimated for year five	7		7
Cost of Sales, Selling and Administrative Expenses and Research and Technical Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ 2	$ 1	$ 5	$ 4
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets			10 years
Maximum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets			25 years
Weighted Average [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets			18 years

Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
	Oct. 01, 2019	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 1,134	$ 1,035	$ 1,152	$ 1,134	$ 1,232	$ 1,134	$ 1,279
Adoption of accounting standards	2
Ending Balance		1,043	1,035	1,152	1,226	1,043	1,226
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(338)	(377)	(302)	(338)		(338)
Other comprehensive income (loss) before reclassifications		31	(78)	43
Amounts reclassified from AOCI		(1)		(1)
Adoption of accounting standards				(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		2	(3)	3
Ending Balance		(349)	(377)	(302)		(349)
Unrealized Gains on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	1			1		1
Adoption of accounting standards				(1)
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(54)	(52)	(52)	(54)		(54)
Other comprehensive income (loss) before reclassifications		(1)
Amounts reclassified from AOCI		2		1
Adoption of accounting standards				1
Ending Balance		(51)	(52)	(52)		(51)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (391)	(429)	(354)	(391)	(315)	(391)	(317)
Other comprehensive income (loss) before reclassifications		30	(78)	43
Amounts reclassified from AOCI		1			2	1	(9)
Adoption of accounting standards				(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		2	(3)	3
Ending Balance		$ (400)	$ (429)	$ (354)	$ (311)	$ (400)	$ (311)

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of AOCI (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
(Gains) Losses Reclassified to Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (2)	$ (1)	$ (4)	$ (4)
(Gains) Losses Excluded from Effectiveness Testing and Amortized to Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax			1	1
Amortization of Actuarial Losses and Prior Service Cost (Credit) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	2	2	3	2
Settlement and Curtailment Gain [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax				(6)
Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		1		(7)
Tax impact	1	1	1	(2)
Total after tax	$ 1	$ 2	$ 1	$ (9)

Commitments and Contingencies - Additional Information (Detail) - Respirator Liabilities [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Sep. 30, 2019
Loss Contingencies [Line Items]
Respirator liability	$ 65.2		$ 65.2
Settlement amount	32.6
Description of pending claims			The Company paid $32.6 million of the settlement during the third quarter of fiscal 2020 and the remaining $32.6 million, which is included in Accounts payable and accrued liabilities on the Consolidated Balance Sheets as of June 30, 2020, will be paid in the first quarter of fiscal 2021.
Respirator reserve	21.0		$ 21.0	$ 35.0
Selling and Administrative Expenses [Member]
Loss Contingencies [Line Items]
Respirator charge		$ 50.0
Accounts Payable and Accrued Liabilities [Member]
Loss Contingencies [Line Items]
Respirator liability	$ 32.6		$ 32.6

Leases - Additional Information (Detail) $ in Millions	3 Months Ended	9 Months Ended
Leases - Additional Information (Detail) $ in Millions	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Lessee Lease Description [Line Items]
Short term lease costs	$ 1	$ 5
Minimum [Member]
Lessee Lease Description [Line Items]
Lease term	1 year	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lease term	19 years	19 years
Lease extension period	15 years	15 years
Variable lease cost	$ 1	$ 1
Maximum [Member] \| Land [Member]
Lessee Lease Description [Line Items]
Lease term	70 years	70 years

Leases - Components of Company's Lease Costs (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Leases [Abstract]
Operating lease cost	$ 7	$ 24
Finance lease cost	2	4
Total lease cost	$ 9	$ 28

Leases - Supplemental Cash Flow Information Related to Company's Leases (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 7	$ 19
Operating cash flows from finance leases		1
Financing cash flows from finance leases	1	2
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 8	13
Right-of-use assets obtained in exchange for new finance lease liabilities		$ 23

Leases - Supplemental Balance Sheet Information Related to Company's Leases (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Oct. 01, 2019
Lease ROU assets:
Operating	$ 102	$ 106
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Finance	$ 45
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet
Total lease ROU assets	$ 147
Lease liabilities:
Operating	$ 17
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Finance	$ 3
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtCurrent
Operating	$ 91
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Finance	$ 28
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtNoncurrent
Total lease liabilities	$ 139

Leases - Weighed Average Remaining Lease Term and Discount Rates (Detail)	Jun. 30, 2020
Lease Cost [Abstract]
Operating leases	16 years
Finance leases	12 years
Operating leases	2.21%
Finance leases	4.44%

Leases - Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Oct. 01, 2019
Operating leases
Remainder of fiscal 2020	$ 6
2021	16
2022	12
2023	10
2024	10
2025 and thereafter	75
Total lease payments	129
Less: imputed interest	21
Operating lease liability	108	$ 111
Finance leases
Remainder of fiscal 2020	1
2021	5
2022	4
2023	4
2024	4
2025 and thereafter	25
Total lease payments	43
Less: imputed interest	12
Total	$ 31

Leases - Future Minimum Lease Payments Under Noncancelable Leases (Detail) $ in Millions	Sep. 30, 2019 USD ($)
Operating leases
2020	$ 23
2021	14
2022	9
2023	9
2024	8
2025 and thereafter	68
Total lease payments	131
Capital leases
2020	3
2021	3
2022	3
2023	3
2024	2
2025 and thereafter	7
Total lease payments	21
Less: imputed interest	9
Total	$ 12

Income Tax - Effective Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
(Provision) benefit for income taxes	$ 5	$ (30)	$ (9)	$ (43)
Effective tax rate	51.00%	43.00%	17.00%	23.00%

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Tax - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Taxes [Line Items]
Net discrete tax (benefits) charges related to tax settlements	$ (2)	$ 13	$ (14)	$ (11)
Changes in uncertain tax positions			8
Net tax benefit related to result of changes in non-us tax laws			6
Net tax expense related to result of changes in us tax laws		17
Uncertain tax positions from expirations of statute of limitations	$ 3	$ 1	$ 11	$ 9
Earliest Tax Year [Member] \| United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2016
Latest Tax Year [Member] \| United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2019
State Tax Authorities [Member] \| Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2005
State Tax Authorities [Member] \| Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2019
Non-U.S. Jurisdictions [Member] \| Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2003
Non-U.S. Jurisdictions [Member] \| Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination			2019

Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic EPS:
Net income (loss) attributable to Cabot Corporation	$ (6)	$ 32	$ 34	$ 124
Earnings (loss) allocated to common shareholders (numerator)	$ (6)	$ 32	$ 34	$ 124
Weighted average common shares and participating securities outstanding	57.2	59.0	57.4	59.9
Less: Participating securities	0.7	0.8	0.7	0.8
Adjusted weighted average common shares (denominator)	56.5	58.2	56.7	59.1
Earnings (loss) per common share - basic:	$ (0.12)	$ 0.55	$ 0.59	$ 2.08
Diluted EPS:
Earnings (loss) allocated to common shareholders	$ (6)	$ 32	$ 34	$ 124
Plus: Earnings allocated to participating securities				1
Less: Adjusted earnings allocated to participating securities				1
Earnings (loss) allocated to common shareholders (numerator)	$ (6)	$ 32	$ 34	$ 124
Adjusted weighted average common shares outstanding	56.5	58.2	56.7	59.1
Common shares issuable		0.2		0.1
Adjusted weighted average common shares (denominator)	56.5	58.4	56.7	59.2
Earnings (loss) per common share - diluted:	$ (0.12)	$ 0.55	$ 0.59	$ 2.08

Earnings Per Share - Calculation of Undistributed Earnings (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) attributable to Cabot Corporation	$ (6)			$ 32			$ 34	$ 124
Less: Dividends declared on common stock	20	$ 20	$ 20	20	$ 20	$ 20	60	60
Undistributed earnings (loss)	(26)			12			(26)	64
Undistributed earnings (loss) allocated to common shareholders	$ (26)			$ 12			$ (26)	$ 64

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Parenthetical) (Detail) - shares	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share	1,853,427	983,081	1,223,055	945,246

Restructuring - Recorded Restructuring Activities (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 3	$ 4	$ 16	$ 15
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense		2	5	7
Selling and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 3	$ 2	$ 11	$ 8

Restructuring - Restructuring Activities and Related Reserves (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2020
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 10	$ 12	$ 7	$ 7
Charges (gain)	3	5	8
Costs charged against assets / (liabilities)		(1)
Cash paid	(4)	(6)	(3)
Reserve balance	9	10	12	9
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	6	8	3	3
Charges (gain)	1	3	7
Cash paid	(2)	(5)	(2)
Reserve balance	5	6	8	5
Accelerated Depreciation and Idle Asset Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges (gain)		1
Costs charged against assets / (liabilities)		(1)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges (gain)	2	1	1
Cash paid	(2)	(1)	(1)
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	4	4	4	4
Reserve balance	$ 4	$ 4	$ 4	$ 4

Restructuring - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ 3	$ 5	$ 8
2020 Reorganization [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs	3				$ 15
Restructuring charges expected in fiscal 2020 related to site demolition and clearing costs	1				1
Restructuring charges expected thereafter fiscal year related to site demolition and clearing costs	5				5
Restructuring cash payments of fiscal year	3				10
Restructuring cash payments through the reminder of fiscal 2020					3
Restructuring future cash payments thereafter fiscal year	7				7
Accrued severance charges	5				5
Purification Solutions Transformation Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments of fiscal year					9		$ 8
Restructuring charges expected	10				10
Restructuring Charges					1		$ 9
Purification Solutions Transformation Plan [Member] \| Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments through the reminder of fiscal 2020					1
Accrued severance charges	$ 1				$ 1
Restructuring Charges				$ 1		$ 9

Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, liabilities, Level 2 to Level 1 transfers, amount	$ 0	$ 0
Fair value, assets, Level 2 to Level 1 transfers, amount	0	0
Fair value, liabilities, Level 1 to Level 2 transfers, amount	0	0
Fair value, assets, Level 1 to Level 2 transfers, amount	0	0
Fair value, assets, transfers into Level 3, amount	0	0
Fair value, assets, transfers out of Level 3, amount	0	0
Fair value, liabilities, transfers into Level 3, amount	0	0
Fair value, liabilities, transfers out of Level 3, amount	0	$ 0
Fair value of long-term debt	1,270,000,000		$ 1,100,000,000
Fixed Rate Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt	1,150,000,000		1,030,000,000.00
Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets in the Consolidated Balance Sheets	11,000,000		10,000,000
Significant Observable Inputs (Level 2) [Member] \| Foreign Currency Risks [Member] \| Prepaid Expenses and Other Current Assets and Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities), at fair Value, net	$ 10,000,000		$ 1,000,000

Derivatives - Details of Derivatives Held to Manage Foreign Currency Risk (Detail)

Jun. 30, 2020

USD ($)

Jun. 30, 2020

EUR (€)

Sep. 30, 2019

USD ($)

Sep. 30, 2019

EUR (€)

Net Investment Hedge [Member] | Cross Currency Swaps [Member]

Derivative [Line Items]

Notional Amount

$ 250,000,000

Net Investment Hedge [Member] | 3.4% Notes [Member] | Cross Currency Swaps [Member]

Derivative [Line Items]

Notional Amount

$ 250,000,000

€ 223,000,000

$ 250,000,000

€ 223,000,000

Net Investment Hedge [Member] | 3.4% Notes [Member] | Fixed Rate Debt [Member] | Cross Currency Swaps [Member]

Derivative [Line Items]

Interest rate on borrowing

3.40%

Not Designated as Hedging Instrument [Member] | Forward Foreign Currency Contracts [Member]

Derivative [Line Items]

Notional Amount

^[1]

$ 32,000,000

$ 54,000,000

[1]	Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna.

Derivatives - Additional Information (Detail) - Cross Currency Swaps [Member] - USD ($)	3 Months Ended
	Dec. 31, 2019	Jun. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Fair value of swaps, net asset		$ 10,000,000	$ 1,000,000
Net Investment Hedge [Member]
Derivative [Line Items]
Notional Amount		250,000,000
Cumulative gain (loss) related to swaps		$ 13,000,000	$ 5,000,000
Net Investment Hedge [Member] \| Fixed Rate Debt [Member]
Derivative [Line Items]
Derivative Instruments Frequency of Cash Settlements	semi-annually

Derivatives - Summary Impact of Cross-currency Swaps to AOCI and Consolidated Statements of Operations (Detail) - Cross Currency Swaps [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) Recognized in AOCI	$ 1	$ (1)	$ 11	$ 12
(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations	$ (2)	$ (1)	(4)	(4)
(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)			$ 1	$ 1

Financial Information by Segment - Additional Information (Detail)	9 Months Ended
	Jun. 30, 2020 Segment
Segment Reporting Information [Line Items]
Number of business reportable segments	3
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Number of business reportable segments	1

Financial Information by Segment - Schedule of Performance Segment (Detail) - Performance Chemicals [Member] - Operating Segments [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net sales	$ 220	$ 251	$ 707	$ 736
Performance Additives [Member]
Segment Reporting Information [Line Items]
Net sales	151	172	489	518
Formulated Solutions [Member]
Segment Reporting Information [Line Items]
Net sales	$ 69	$ 79	$ 218	$ 218

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

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-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues from external customers	$ 518	$ 845	$ 1,955	$ 2,510
Income (loss) before income taxes	(11)	69	51	188
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	480	798	1,824	2,365
Income (loss) before income taxes	18	112	199	329
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	38	47	131	145
Income (loss) before income taxes	(29)	(43)	(148)	(141)
Reinforcement Materials [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	197	461	931	1,363
Income (loss) before income taxes	(5)	72	103	195
Performance Chemicals [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	220	251	707	736
Income (loss) before income taxes	21	37	93	111
Purification Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	63	73	186	210
Income (loss) before income taxes	$ 2	1	$ 3	(1)
Specialty Fluids [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		13		56
Income (loss) before income taxes		$ 2		$ 24

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Section S99
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-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%	100.00%	100.00%

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable and By-product Revenue (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenues from external customers	$ 518	$ 845	$ 1,955	$ 2,510
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	38	47	131	145
Unallocated and Other [Member] \| Royalties, the Impact of Unearned Revenue, the Removal of 100% of the Sales of an Equity Method Affiliate and Discounting Charges for Certain Notes Receivable [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	4	(3)	2	(9)
Unallocated and Other [Member] \| Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	22	32	83	96
Unallocated and Other [Member] \| By-product Sales [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 12	$ 18	$ 46	$ 58

- Definition

+ References

+ Details

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable and By-product Revenue (Parenthetical) (Detail)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%	100.00%	100.00%

Financial Information by Segment - Schedule of Income (Loss) from Continuing Operations before Income Taxes and Equity in Earnings of Affiliated Companies for Unallocated and Other (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Interest expense	$ (13)	$ (14)	$ (41)	$ (43)
Global restructuring activities	(3)	(4)	(16)	(15)
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(13)	(14)	(41)	(43)
Unallocated corporate costs	(10)	(14)	(32)	(39)
General unallocated income (expense)	2		1	3
Less: Equity in earnings of affiliated companies, net of tax	1	1	2	1
Income from continuing operations before income taxes and equity in earnings of affiliated companies	(29)	(43)	(148)	(141)
Certain Items [Member]
Segment Reporting Information [Line Items]
Legal and environmental matters and reserves	(1)		(51)	(1)
Global restructuring activities	(3)	(4)	(16)	(15)
Employee benefit plan settlements	(2)		(5)	3
Acquisition and integration-related charges	(1)	(1)	(3)	(5)
Indirect tax settlement credits			3
Other		(1)	(1)	(4)
Total certain items, pre-tax	$ (7)	(14)	(74)	(61)
Certain Items [Member] \| Equity Affiliate Investment [Member]
Segment Reporting Information [Line Items]
Investment impairment charge				(11)
Certain Items [Member] \| Specialty Fluids [Member]
Segment Reporting Information [Line Items]
Loss on sale and asset impairment charges		$ (8)	$ (1)	$ (28)

Financial Information by Segment - Revenue from External Customers by Geographic Region (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 518	$ 845	$ 1,955	$ 2,510
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	480	798	1,824	2,365
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	38	47	131	145
Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	141	283	643	836
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	212	294	695	853
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	127	221	486	676
Reinforcement Materials [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	197	461	931	1,363
Reinforcement Materials [Member] \| Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	59	179	354	515
Reinforcement Materials [Member] \| Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	106	191	398	573
Reinforcement Materials [Member] \| Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	32	91	179	275
Performance Chemicals [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	220	251	707	736
Performance Chemicals [Member] \| Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	54	69	206	222
Performance Chemicals [Member] \| Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	98	93	271	253
Performance Chemicals [Member] \| Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	68	89	230	261
Purification Solutions [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	63	73	186	210
Purification Solutions [Member] \| Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	28	33	83	93
Purification Solutions [Member] \| Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	8	10	26	26
Purification Solutions [Member] \| Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 27	30	$ 77	91
Specialty Fluids [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		13		56
Specialty Fluids [Member] \| Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		2		6
Specialty Fluids [Member] \| Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues				1
Specialty Fluids [Member] \| Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		$ 11		$ 49