Cabot (CBT) 10-K 22 Nov 23 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2023	Nov. 13, 2023	Mar. 31, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	CBT
Entity Registrant Name	Cabot Corporation
Entity Central Index Key	0000016040
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		55,309,058
Entity Public Float			$ 4,276,465,633
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Entity File Number	1-5667
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-2271897
Entity Address, Address Line One	Two Seaport Lane
Entity Address, Address Line Two	Suite 1400
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02210
City Area Code	617
Local Phone Number	345-0100
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $1 par value per share
Security Exchange Name	NYSE
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	Boston, Massachusetts

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Net sales and other operating revenues	$ 3,931	$ 4,321	$ 3,409
Cost of sales	3,092	3,436	2,610
Gross profit	839	885	799
Selling and administrative expenses	253	258	289
Research and technical expenses	57	55	56
Loss on sale of business and asset impairment charge	3	207
Gain on bargain purchase of a business (Note C)		(24)
Income (loss) from operations	526	389	454
Interest and dividend income	31	11	8
Interest expense	(90)	(56)	(49)
Other income (expense)	(16)	(9)	(7)
Income (loss) from operations before income taxes and equity in earnings of affiliated companies	451	335	406
(Provision) benefit for income taxes	28	(102)	(123)
Equity in earnings of affiliated companies, net of tax	5	10	3
Net income (loss)	484	243	286
Net income (loss) attributable to noncontrolling interests, net of tax of $9, $8 and $10	39	34	36
Net income (loss) attributable to Cabot Corporation	$ 445	$ 209	$ 250
Weighted-average common shares outstanding:
Basic	56.1	56.5	56.7
Diluted	56.5	56.9	56.8
Earnings (loss) per common share:
Basic	$ 7.79	$ 3.65	$ 4.35
Diluted	$ 7.73	$ 3.62	$ 4.34
Purification Solutions [Member]
Loss on sale of business and asset impairment charge		$ 197

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Net income attributable to noncontrolling interests, tax amount	$ 9	$ 8	$ 10

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 484	$ 243	$ 286
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax	80	(175)	52
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax	(6)	(6)	(5)
(Gains) losses excluded from effectiveness testing and amortized to interest expense, net of tax	2	2	2
Pension and other postretirement benefit liability adjustments, net of tax	1	14	20
Other comprehensive income (loss), net of tax of $1, $3 and $8	77	(165)	69
Comprehensive income (loss)	561	78	355
Net Income (Loss) Attributable to Noncontrolling Interest	39	34	36
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax		(15)	7
Comprehensive income (loss) attributable to noncontrolling interests	39	19	43
Comprehensive income (loss) attributable to Cabot Corporation	$ 522	$ 59	$ 312

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net of tax	$ 1	$ 3	$ 8

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Current assets:
Cash and cash equivalents	$ 238	$ 206
Accounts and notes receivable, net of reserve for doubtful accounts of $2 and $3	695	836
Inventories	585	664
Prepaid expenses and other current assets	108	114
Total current assets	1,626	1,820
Property, plant and equipment	3,827	3,554
Accumulated depreciation	(2,415)	(2,284)
Net property, plant and equipment	1,412	1,270
Goodwill	134	129
Equity affiliates	20	20
Intangible assets, net	60	63
Deferred income taxes	180	45
Other assets	172	178
Total assets	3,604	3,525
Current liabilities:
Short-term borrowings	174	347
Accounts payable and accrued liabilities	600	707
Income taxes payable	40	44
Current portion of long-term debt	8	7
Total current liabilities	822	1,105
Long-term debt	1,094	1,089
Deferred income taxes	50	65
Other liabilities	231	234
Commitments and contingencies (Note S)
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: 55,379,636 and 56,385,963 shares, Outstanding: 55,243,804 and 56,248,559 shares	55	56
Less cost of xxx,xxx and 137,404 shares of common treasury stock	(3)	(4)
Additional paid-in capital		1
Retained earnings	1,574	1,284
Accumulated other comprehensive income (loss)	(362)	(439)
Total Cabot Corporation stockholders’ equity	1,264	898
Noncontrolling interests	143	134
Total stockholders’ equity	1,407	1,032
Total liabilities and stockholders’ equity	$ 3,604	$ 3,525

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
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	55,379,636	56,385,963
Common stock, outstanding shares	55,243,804	56,248,559
Common treasury stock, shares	135,832	137,404

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash Flows from Operating Activities:
Net income (loss)	$ 484	$ 243	$ 286
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	144	146	160
Loss on sale of business and asset impairment charge	3	207
Gain on bargain purchase of a business		(24)
Gain on sale of land	(1)	(17)
Deferred tax provision (benefit)	(156)	(40)	9
Employee benefit plan settlement		(1)	5
Equity in net income of affiliated companies	(5)	(10)	(3)
Stock-based compensation	20	23	21
Other non-cash (income) expense	4	20	21
Cash dividends received from equity affiliates	2	1	2
Changes in assets and liabilities:
Accounts and notes receivable	153	(287)	(215)
Inventories	96	(259)	(174)
Prepaid expenses and other current assets	1	(25)	(37)
Accounts payable and accrued liabilities	(152)	115	167
Income taxes payable	(4)	15	14
Other liabilities	6	(7)	1
Cash provided by operating activities	595	100	257
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(244)	(211)	(195)
Proceeds from sale of a business	6	79
Cash paid for acquisition of business, net of cash acquired of $-, $5 and $-		(9)
Proceeds from sale of land	7	18
Proceeds from insurance settlements	12	1	2
Other	5	4	7
Cash used in investing activities	(214)	(118)	(186)
Cash Flows from Financing Activities:
Proceeds from short-term borrowings	24	26
Repayments of short-term borrowings	(48)
Proceeds from (repayments of) issuance of commercial paper, net	(149)	250	58
Proceeds from long-term debt, net of issuance costs	84	394	200
Repayments of long-term debt	(90)	(372)	(222)
Purchases of common stock	(98)	(53)	(3)
Proceeds from sales of common stock	4	6	6
Cash dividends paid to noncontrolling interests	(42)	(22)	(19)
Cash dividends paid to common stockholders	(88)	(84)	(80)
Cash provided by (used in) financing activities	(403)	145	(60)
Effects of exchange rate changes on cash	54	(91)	8
Increase (decrease) in cash, cash equivalents and restricted cash	32	36	19
Cash, cash equivalents and restricted cash at beginning of year	206	170	151
Cash, cash equivalents and restricted cash at end of year	238	206	170
The following table presents the Company’s cash, cash equivalents and restricted cash by category within the Consolidated Balance Sheets:
Cash and cash equivalents	$ 238	$ 206	168
Restricted cash classified within Prepaid expenses and other current assets			$ 2
Restricted Cash and Cash Equivalents, Current, Statement of Financial Position [Extensible Enumeration]	PrepaidExpensesAndOtherCurrentAssets	PrepaidExpensesAndOtherCurrentAssets	PrepaidExpensesAndOtherCurrentAssets
Cash, cash equivalents and restricted cash	$ 238	$ 206	$ 170
Non-cash investing activities and supplemental cash flow information:
Additions to property, plant and equipment included in Accounts payable and accrued liabilities	41	24	41
Income taxes paid	140	129	93
Interest paid	$ 85	$ 46	$ 41

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) $ in Millions	12 Months Ended
	Sep. 30, 2022 USD ($)
Statement Of Cash Flows [Abstract]
Cash acquired in acquisition of business	$ 5

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - 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, 2020	$ 814	$ 53		$ 989	$ (351)	$ 691	$ 123
Beginning Balance, Shares at Sep. 30, 2020		56,467
Net income (loss)	286			250		250	36
Total other comprehensive income (loss)	69				62	62	7
Cash dividends declared to noncontrolling interests	(23)						(23)
Cash dividends declared, Common stock, per share	(80)			(80)		(80)
Issuance of stock under equity compensation plans	6		$ 6			6
Issuance of stock under equity compensation plans, Shares		317
Stock-based compensation	21		21			21
Purchase and retirement of common stock	(3)		(3)			(3)
Purchase and retirement of common stock, Shares		(57)
Ending Balance at Sep. 30, 2021	1,090	$ 53	24	1,159	(289)	947	143
Ending Balance, Shares at Sep. 30, 2021		56,727
Net income (loss)	243			209		209	34
Total other comprehensive income (loss)	(165)				(150)	(150)	(15)
Cash dividends declared to noncontrolling interests	(28)						(28)
Cash dividends declared, Common stock, per share	(84)			(84)		84
Issuance of stock under equity compensation plans	6		6			6
Issuance of stock under equity compensation plans, Shares		359
Stock-based compensation	23		23			23
Purchase and retirement of common stock	(53)	$ (1)	(52)			(53)
Purchase and retirement of common stock, Shares		(837)
Ending Balance at Sep. 30, 2022	1,032	$ 52	1	1,284	(439)	898	134
Ending Balance, Shares at Sep. 30, 2022		56,249
Net income (loss)	484			445		445	39
Total other comprehensive income (loss)	77				77	77
Cash dividends declared to noncontrolling interests	(30)						(30)
Cash dividends declared, Common stock, per share	(88)			(88)		(88)
Issuance of stock under equity compensation plans	4	$ 1	3			4
Issuance of stock under equity compensation plans, Shares		357
Stock-based compensation	26		26			26
Purchase and retirement of common stock	(98)	$ (1)	$ (30)	(67)		(98)
Purchase and retirement of common stock, Shares		(1,362)
Ending Balance at Sep. 30, 2023	$ 1,407	$ 52		$ 1,574	$ (362)	$ 1,264	$ 143
Ending Balance, Shares at Sep. 30, 2023		55,244

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Stockholders' Equity [Abstract]
Cash dividends declared, per share	$ 1.54	$ 1.48	$ 1.40

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 445	$ 209	$ 250

Insider Trading Arrangements

Insider Trading Arrangements	12 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Significant Accounting Policies	Note A. Significant Accounting Policies The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”). The significant accounting policies of Cabot Corporation (“Cabot” or “the Company”) are described below. Unless otherwise indicated, all disclosures and amounts in the Notes to the Consolidated Financial Statements relate to the Company’s operations. Principles of Consolidation The consolidated financial statements include the accounts of Cabot and its wholly-owned subsidiaries and majority-owned and controlled subsidiaries. Additionally, Cabot considers consolidation of entities over which control is achieved through means other than voting rights, of which there were none in the periods presented. Intercompany transactions have been eliminated in consolidation. Cash and Cash Equivalents Cash equivalents include all highly liquid investments with a maturity of three months or less at date of acquisition. Cabot continually assesses the liquidity of cash equivalents and, as of September 30, 2023, has determined that they are readily convertible to cash. Inventories Inventories are stated at the lower of cost or net realizable value. The cost of inventories is determined using the first-in, first-out 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. Investments The Company has investments in equity affiliates and marketable securities. As circumstances warrant, all investments are subject to periodic impairment reviews. Unless consolidation is required, investments in equity affiliates, where Cabot generally owns between 20 % and 50 % of the affiliate, are accounted for using the equity method. Cabot records its share of the equity affiliate’s results of operations based on its percentage of ownership of the affiliate. Dividends declared from equity affiliates are a return on investment and are recorded as a reduction to the equity investment value. At both September 30, 2023 and 2022, Cabot had equity affiliate investments of $ 20 million. Dividends declared and received from these investments were $ 2 million, $ 1 million and $ 5 million in fiscal 2023, 2022 and 2021, respectively. 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 an acquisition are allocated to the assets acquired and liabilities assumed 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 and is subject to impairment testing annually, 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, specialty carbons and battery materials product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of September 30, 2023. 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. 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 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. The fair value is also benchmarked against the value calculated from a market approach using the guideline public company method. In fiscal 2023, the Company’s qualitative assessment, performed as of August 31, 2023, indicated that the fair values of the Reinforcement Materials, fumed metal oxides, specialty compounds, specialty carbons and battery materials reporting units were in excess of their carrying values. Long-lived Assets Impairment Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable. 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. 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 market value, a discounted cash flow model may be used to determine the fair value of the asset. 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 generally 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. Cabot capitalizes interest costs when they are part of the cost of acquiring and constructing certain assets that require a period of time to prepare for their intended use. During fiscal 2023, 2022 and 2021, Cabot capitalized $ 6 million, $ 3 million and $ 1 million of interest costs, respectively. These amounts are amortized over the lives of the related assets when they are placed in service. Asset Retirement Obligations Cabot estimates incremental costs for special handling, removal and disposal of materials that may or will give rise to conditional asset retirement obligations (“ARO”) and then discounts the expected costs back to the current year using a credit adjusted risk-free rate. Cabot recognizes ARO liabilities and costs when they are probable and can be reasonably estimated. In certain instances, Cabot has not recorded a reserve for AROs because the timing of disposal of the underlying asset is unknown. The ARO reserves were $ 11 million and $ 10 million at September 30, 2023 and 2022, respectively. The ARO balances are included in Accounts payable and accrued liabilities and Other liabilities on the Consolidated Balance Sheets. Foreign Currency Translation The functional currency of the majority of Cabot’s foreign subsidiaries is the local currency in which the subsidiary operates. Assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet dates. Income and expense items are translated at average monthly exchange rates during the year. The functional currency of Cabot’s foreign subsidiaries that operate in a highly inflationary economy is the U.S. dollar. Cabot’s operations in highly inflationary economies are not material. Unrealized currency translation adjustments (“CTA”) are included as a separate component of Accumulated other comprehensive income (loss) (“AOCI”) within stockholders’ equity. Realized and unrealized foreign currency gains and losses arising from transactions denominated in currencies other than the subsidiary’s functional currency are reflected in earnings with the exception of (i) intercompany transactions considered to be of a long-term investment nature; (ii) income taxes upon future repatriation of unremitted earnings from non-U.S. subsidiaries that are not indefinitely reinvested; and (iii) foreign currency borrowings designated as net investment hedges. Gains or losses arising from these transactions are included within the CTA component of Other comprehensive income (loss). In fiscal 2023, 2022 and 2021, net foreign currency transaction loss of $ 35 million, $ 13 million, and $ 6 million, respectively, is included in Other income (expense) in the Consolidated Statements of Operations. Share Repurchases Periodically, Cabot repurchases shares of the Company’s common stock in the open market or in privately negotiated transactions under the authorization approved by the Board of Directors. The Company retires the repurchased shares and records the excess of the purchase price over par value to additional paid-in capital (“APIC”) until such amount is reduced to zero and then charges the remainder against retained earnings. Financial Instruments Cabot’s financial instruments consist primarily of cash and cash equivalents, accounts and notes receivable, investments, accounts payable and accrued liabilities, short-term and long-term debt, and derivative instruments. The carrying values of Cabot’s financial instruments approximate fair value with the exception of fixed rate long-term debt, which is recorded at amortized cost. The fair values of the Company’s financial instruments are based on quoted market prices, if such prices are available. In situations where quoted market prices are not available, the Company relies on valuation models to derive fair value. Such valuations take into account the ability of the financial counterparty to perform and the Company’s own credit risk. Cabot uses derivative financial instruments primarily for purposes of hedging the exposures to fluctuations in foreign currency exchange rates, which exist as part of its on-going business operations. Cabot does not enter into derivative contracts for speculative purposes, nor does it hold or issue any derivative contracts for trading purposes. All derivatives are recognized on the Consolidated Balance Sheets at fair value. Where Cabot has a legal right to offset derivative settlements under a master netting agreement with a counterparty, derivatives with that counterparty are presented on a net basis. The changes in the fair value of derivatives are recorded in either earnings or AOCI, depending on whether or not the instrument is designated as part of a hedge transaction and, if designated as part of a hedge transaction, the type of hedge transaction. The gains or losses on derivative instruments reported in AOCI are reclassified to earnings in the period in which earnings are affected by the underlying hedged item. The ineffective portion of all hedges is recognized in earnings during the period in which the ineffectiveness occurs. In accordance with Cabot’s risk management strategy, the Company may enter into certain derivative instruments that may not be designated as hedges for hedge accounting purposes. Although these derivatives are not designated as hedges, the Company believes that such instruments are closely correlated with the underlying exposure, thus managing the associated risk. The Company records in earnings the gains or losses from changes in the fair value of derivative instruments that are not designated as hedges. Cash movements associated with these instruments are presented in the Consolidated Statements of Cash Flows as Cash Flows from Operating Activities because the derivatives are designed to mitigate risk to the Company’s cash flow from operations. Revenue Recognition Cabot recognizes revenue when its customers obtain control of promised goods or services. The revenue recognized is the amount of consideration which 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. Substantially all revenue from product sales is based on a point in time model and is recognized 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. For contracts where we complete our performance obligation prior to our right to consideration or contracts where we receive consideration prior to completing our performance obligation we record a contract asset or a contract liability, respectively, on the Consolidated Balance Sheets. Shipping and handling activities that occur after the transfer of control to the customer are billed to customers and are recorded as sales revenue, as the Company considers these to be fulfillment costs. These 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. Payment terms typically range from zero to ninety days . 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. Cost of Sales Cost of sales consists of the cost of raw and packaging materials, direct manufacturing costs, depreciation, internal transfer costs, inspection costs, inbound and outbound freight and shipping and handling costs, plant purchasing and receiving costs and other overhead expenses necessary to manufacture the products. Accounts and Notes Receivable Trade receivables are recorded at the invoiced amount and generally do not bear interest. Cabot maintains allowances for doubtful accounts based on an assessment of the collectability of specific customer accounts, the aging of accounts receivable and other economic information on both a historical and prospective basis. Customer account balances are charged against the allowance when it is probable the receivable will not be recovered. There were no material changes in the allowance for any of the years presented. Stock-based Compensation Cabot recognizes compensation expense for stock-based awards granted to employees using the fair value method. Under the fair value recognition provisions, stock-based compensation cost is measured at the grant date based on the fair value of the award, and is recognized as expense over the service period, which generally represents the vesting period, and includes an estimate of what level of performance the Company will achieve for Cabot’s performance-based stock awards. Cabot calculates the fair value of its stock options using the Black-Scholes option pricing model. The fair value of restricted stock units is determined using the closing price of Cabot stock on the day of the grant. The Company recognizes forfeitures as they occur. Selling and Administrative Expenses Selling and administrative expenses consist of salaries and fringe benefits of sales and office personnel, general office expenses and other expenses not directly related to manufacturing operations. Research and Technical Expenses Research and technical expenses include salaries, equipment and material expenditures, and contractor fees and are expensed as incurred. 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. Service cost is included with other employee compensation costs within Cost of sales, Selling and administrative expenses, or Research and technical expenses. The Company recognizes actuarial gains and losses and prior service costs and credits as a component of Other comprehensive income (loss), net of tax, which are subsequently amortized into earnings as a component of net periodic benefit cost. 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 and pension and post-retirement related adjustments. Income Taxes Deferred income taxes are determined based on the estimated future tax effects of differences between financial statement carrying amounts and the tax bases of existing assets and liabilities. Deferred tax assets are recognized to the extent that realization of those assets is considered to be more likely than not. A valuation allowance is established for deferred taxes when it is more likely than not that all or a portion of the deferred tax assets will not be realized. Provisions are made for the U.S. income tax liability and additional non-U.S. taxes on the undistributed earnings of non-U.S. subsidiaries, except for amounts Cabot has designated to be indefinitely reinvested. Cabot records benefits for uncertain tax positions based on an assessment of whether the position is more likely than not to be sustained by the taxing authorities. If this threshold is not met, no tax benefit of the uncertain tax position is recognized. If the threshold is met, the tax benefit that is recognized is the largest amount that is greater than 50 % likely of being realized upon ultimate settlement. This analysis presumes the taxing authorities’ full knowledge of the positions taken and all relevant facts, but does not consider the time value of money. The Company also accrues for interest and penalties on its uncertain tax positions and includes such charges in its income tax provision in the Consolidated Statements of Operations. Contingencies Cabot accrues costs related to contingencies when it is probable that a liability has been incurred and the amount can be reasonably estimated. Contingencies could arise from litigation, environmental remediation or contractual arrangements. When a single liability amount cannot be reasonably estimated, but a range can be reasonably estimated, Cabot accrues the amount that reflects the best estimate within that range or the low end of the range if no estimate within the range would be considered more likely than any other estimate. The amount accrued is determined through the evaluation of various information, which could include claims, settlement offers, demands by government agencies, estimates performed by independent third parties, identification of other responsible parties and an assessment of their ability to contribute, and our prior experience. Cabot does not reduce its estimated liability for possible recoveries from insurance carriers. Proceeds from insurance carriers are recorded when realized by either the receipt of cash or a contractual agreement. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amount of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Sep. 30, 2023
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Note B. Recent Accounting Pronouncements In November 2022, the FASB issued a new standard on the disclosure of supplier financing programs. The new standard requires qualitative and quantitative disclosure as to the nature and potential magnitude of such programs in addition to program activity and changes for the periods presented. The Company adopted this standard October 1, 2023. The Company has evaluated the effect of adopting this accounting guidance and will include the new required disclosure in future filings.

Acquisitions

Acquisitions	12 Months Ended
	Sep. 30, 2023
Business Combinations [Abstract]
Acquisitions	Note C. Acquisitions Tokai Carbon (Tianjin) Co. In February 2022, the Company purchased 100 % of the registered capital of Tokai Carbon (Tianjin) Co., a carbon black manufacturing facility, from Tokai Carbon Group for a net purchase price of $ 9 million, consisting of cash consideration of $ 14 million, including customary post-closing adjustments, and net of $ 5 million of cash acquired. The excess of the fair value of the net assets over the purchase price was recorded as a gain of $ 24 million in fiscal 2022. The Gain on bargain purchase of a business arose primarily due to necessary equipment upgrades that will be required after the purchase to continue to utilize the existing assets.

Divestitures

Divestitures	12 Months Ended
	Sep. 30, 2023
Discontinued Operations and Disposal Groups [Abstract]
Divestitures	Note D. Divestitures Sale of Purification Solutions Business In March 2022, the Company completed the sale of its Purification Solutions business, a reporting segment of the Company, to an affiliate of funds advised by One Equity Partners for total cash proceeds of $ 85 million, net of $ 7 million cash transferred. The Company recognized a pre-tax impairment charge of $ 197 million and a pre-tax loss on sale of the Purification Solutions business of $ 10 million during fiscal 2022. The purchase price of the Purification Solutions business was subject to customary post-closing adjustments, which were finalized in fiscal 2023 and resulted in an additional pre-tax loss on sale of $ 3 million.

Inventories

Inventories	12 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories	Note E. Inventories Inventories, net of obsolete, unmarketable and slow-moving reserves, are as follows: September 30 2023 2022 (In millions) Raw materials $ 148 $ 182 Finished goods 374 427 Other (1) 63 55 Total $ 585 $ 664 (1) Other inventory is comprised of certain spare parts and supplies. At September 30, 2023 and 2022, total inventory reserves were $ 14 million and $ 9 million, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Sep. 30, 2023
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	Note F. Property, Plant and Equipment Property, plant and equipment consists of the following: September 30 2023 2022 (In millions) Land and land improvements $ 72 $ 75 Buildings 576 553 Machinery and equipment 2,622 2,473 Other 228 229 Construction in progress 329 224 Total property, plant and equipment 3,827 3,554 Less: Accumulated depreciation ( 2,415 ) ( 2,284 ) Net property, plant and equipment $ 1,412 $ 1,270 Depreciation expense for fiscal 2023, 2022 and 2021 was $ 138 million, $ 140 million and $ 152 million, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Note G. 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 fiscal year ended September 30, 2023 are as follows : Reinforcement Performance Total (In millions) Balance at September 30, 2022 $ 46 $ 83 $ 129 Foreign currency impact 5 — 5 Balance at September 30, 2023 $ 51 $ 83 $ 134 The following table provides information regarding the Company’s intangible assets with finite lives: September 30, 2023 September 30, 2022 Gross Accumulated Net Gross Accumulated Net (In millions) Developed technologies $ 34 $ ( 10 ) $ 24 $ 34 $ ( 8 ) $ 26 Trademarks 2 ( 1 ) 1 2 ( 1 ) 1 Customer relationships 65 ( 30 ) 35 59 ( 23 ) 36 Total intangible assets $ 101 $ ( 41 ) $ 60 $ 95 $ ( 32 ) $ 63 Intangible assets are amortized over their estimated useful lives, which range between ten and twenty-five years , with a weighted average amortization period of seventeen years . Amortization expense for fiscal 2023, 2022 and 2021 was $ 6 million, $ 6 million and $ 8 million, respectively, and 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 $ 6 million each year for the next five fiscal years.

Accounts Payable, Accrued Liabi

Accounts Payable, Accrued Liabilities and Other Liabilities	12 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Accounts Payable, Accrued Liabilities and Other Liabilities	Note H. Accounts Payable, Accrued Liabilities and Other Liabilities Accounts payable and accrued liabilities included in current liabilities consist of the following: September 30 2023 2022 (In millions) Accounts payable $ 438 $ 533 Accrued employee compensation 55 66 Other accrued liabilities 107 108 Total $ 600 $ 707 Other long-term liabilities consist of the following: September 30 2023 2022 (In millions) Employee benefit plan liabilities $ 48 $ 51 Operating lease liabilities 84 83 Other accrued liabilities 99 100 Total $ 231 $ 234

Debt and Other Obligations

Debt and Other Obligations	12 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Debt and Other Obligations	Note I. Debt and Other Obligations Short-term Borrowings Commercial Paper — The Company has a commercial paper program and the maximum aggregate balance of commercial paper notes outstanding and the amounts borrowed under the revolving credit facility may not exceed the borrowing capacity of $ 1 billion under the revolving credit facility. The proceeds from the issuance of the commercial paper have been used for general corporate purposes, which may include working capital, refinancing existing indebtedness, capital expenditures, share repurchases, and acquisitions. The revolving credit facility is available to repay the outstanding commercial paper, if necessary. There was an outstanding balance of commercial paper of $ 172 million as of September 30, 2023 with a weighted average interest rate of 5.44 % and an outstanding balance of $ 322 million as of September 30, 2022 with a weighted average interest rate of 3.35 %. Long-term Obligations The Company’s long-term obligations, the fiscal year in which they mature and their respective interest rates are summarized below: September 30 2023 2022 (In millions) Variable Rate Debt: Revolving Credit Facility, expires fiscal 2027 $ — $ — Revolving Credit Facility - Euro, expires fiscal 2027 120 114 Total variable rate debt 120 114 Fixed Rate Debt: 3.4 % Notes due fiscal 2026 250 250 4.0 % Notes due fiscal 2029 300 300 5.0 % Notes due fiscal 2032 400 400 Medium-Term Notes due fiscal 2028 , 6.57 % — 7.28 % 8 8 Chinese Renminbi Debt, due fiscal 2024 , 4.3 % 4 4 Total fixed rate debt 962 962 Finance lease obligations (Note R) 28 29 Unamortized debt issuance costs and debt discount ( 8 ) ( 9 ) Total debt 1,102 1,096 Less current portion of long-term debt ( 8 ) ( 7 ) Total long-term debt $ 1,094 $ 1,089 Revolving Credit Facility, expiring fiscal 2027 — In August 2021, the Company entered into a revolving credit agreement (the “U.S. Credit Agreement”) with a loan commitment not to exceed $ 1 billion. The U.S. Credit Agreement supports the Company’s issuance of commercial paper, and borrowings may be used for working capital, letters of credit and other general corporate purposes. Outstanding commercial paper balances reduce the amount available for borrowing under the U.S. Credit Agreement, which was $ 828 million as of September 30, 2023. The U.S. Credit Agreement, which matures in August 2027 , contains affirmative and negative covenants, the financial debt covenant described below, and annual sustainability performance targets related to the Company’s reduction in its nitrogen oxide and sulfur dioxide emissions intensity, the achievement of which may adjust pricing under the U.S. Credit Agreement. The borrowing rate is currently based on an adjusted daily risk-free borrowing rate, plus a Cabot-specific spread based on the Company’s credit rating and achievement on the annual sustainability performance targets. As a result of meeting the annual sustainability performance targets, the commitment fee and borrowing rate will be reduced by 0.01 % and 0.05 %, respectively, effective from August 2023 through August 2024. Revolving Credit Facility-Euro, expiring fiscal 2027 —In May 2023, several subsidiaries entered into a revolving credit agreement (the “Euro Credit Agreement”, and together with the U.S. Credit Agreement, the "Credit Agreements") with a loan commitment not to exceed 300 million Euros. The amount available for borrowing under this revolving credit agreement was $ 197 million as of September 30, 2023, and the weighted average interest rate on the outstanding balance during the year was 4.82 %. The borrowing rate is based on an adjusted daily risk-free borrowing rate, plus a Cabot-specific spread based on the Company’s credit rating. The revolving credit agreement, which matures in August 2027 , may be used for repatriation of earnings of Cabot’s foreign subsidiaries to the U.S., the repayment of indebtedness of the Company’s foreign subsidiaries owing to the Company or any of its subsidiaries, and for working capital and general corporate purposes. The obligations of the subsidiaries under the revolving credit agreement are guaranteed by the Company. The Company paid debt issuance costs of $ 1 million upon entering the agreement, which are being amortized over the life of the revolver. Debt Covenants —As of September 30, 2023, Cabot was in compliance with the financial debt covenants under the Credit Agreements, which, with limited exceptions, require us to comply on a quarterly basis with a leverage test requiring the ratio of consolidated net debt to consolidated EBITDA not to exceed 3.50 to 1.00 . Consolidated net debt is defined as consolidated debt offset by the lessor of (i) unrestricted cash and cash equivalents and (ii) $ 150 million. Chinese Renminbi Debt — The Company’s consolidated Chinese subsidiaries had $ 4 million of unsecured long-term debt outstanding with a noncontrolling shareholder of a consolidated subsidiary as of both September 30, 2023 and 2022. 3.4% Notes due fiscal 2026 —In September 2016, Cabot issued $ 250 million in registered notes with a coupon of 3.4 % that mature on September 15, 2026 . These notes are unsecured and pay interest on March 15 and September 15. The net proceeds of this offering were $ 248 million after deducting discounts and issuance costs. The discount of less than $ 1 million was recorded at issuance and is being amortized over the life of the notes. 4.0% Notes due fiscal 2029 —In June 2019, Cabot issued $ 300 million in registered, unsecured, notes with a coupon of 4.0 % that mature on July 1, 2029 . Interest is payable under the notes semi-annually on January 1 and July 1. The net proceeds of this offering were $ 296 million after deducting discounts and issuance costs of $ 1 million and $ 3 million, respectively, which were paid at issuance and are being amortized over the life of the notes. 5.0% Notes due fiscal 2032 — In June 2022, Cabot issued $ 400 million in unsecured notes with a coupon of 5 % that mature on June 30, 2032 . Interest is payable semi-annually on June 30 and December 30. The net proceeds of this offering were $ 394 million after deducting discounts and issuance costs, each of which were $ 3 million, which were paid at issuance and are being amortized over the life of the notes. Medium-Term Notes —At both September 30, 2023 and 2022, there were $ 8 million of unsecured medium-term notes outstanding issued to numerous lenders with various fixed interest rates and maturity dates. The weighted average maturity of the total outstanding medium-term notes is 4 years with a weighted average interest rate of 7.24 %. Finance Lease obligations —See Note R for a discussion of the Company’s leases. Future Years Payment Schedule The aggregate principal amounts of long-term debt, excluding finance lease liabilities presented separately in Note R, due in each of the five years from fiscal 2024 through 2028 and thereafter are as follows: Years Ending September 30 Principal Payments (In millions) 2024 $ 4 2025 — 2026 250 2027 120 2028 8 Thereafter 700 Total $ 1,082 Standby letters of credit —A t September 30, 2023, the Company had provided standby letters of credit that were outstanding and not drawn totaling $ 7 million, which expire through fiscal 2024 .

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	12 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	Note J. 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 fiscal 2023 or 2022. At both September 30, 2023 and 2022, 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. Cash and cash equivalents are classified as Level 1 within the fair value hierarchy. At both September 30, 2023 and 2022, Cabot had derivatives relating to foreign currency risks carried at fair value. The Company uses standard models with market-based inputs, which take into account the present value of estimated future cash flows and the ability of Cabot or the financial counterparty to perform. For interest rate and cross-currency swaps, the significant inputs to these models are interest rate curves for discounting future cash flows and are adjusted for credit risk. For forward foreign currency contracts, the significant inputs are interest rate curves for discounting future cash flows, and exchange rate curves of the foreign currency for translating future cash flows. These derivatives are classified as Level 2 instruments within the fair value hierarchy as the fair value determination was based on observable inputs. At both September 30, 2023 and 2022, the fair value of Guaranteed investment contracts, included in Other assets on the Consolidated Balance Sheets was $ 8 million. 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. The carrying value and fair value of the long-term fixed rate debt were $ 1.08 billion and $ 1.04 billion, respectively, as of September 30, 2023 and $ 1.08 billion and $ 1.06 billion, respectively, as of September 30, 2022. 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 approximates the fair value. 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

Derivatives	12 Months Ended
	Sep. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives	Note K. Derivatives The Company has foreign currency exposure arising from its net investments in foreign operations. The Company uses cross-currency swaps to partially mitigate the impact of the Euro currency rate changes on the Company’s Euro denominated net investments. The Company’s cross-currency swaps are designated as net investment hedges. 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. The Company uses short-term forward contracts to minimize the exposure to foreign currency risk. The Company had no significant concentration of credit risk at September 30, 2023 and 2022. The following table provides details of the derivatives held as of September 30, 2023 and 2022 to manage foreign currency risk. Notional Amount Description Borrowing September 30, 2023 September 30, 2022 Hedge 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 82 million USD 42 million No designation (1) At September 30, 2023, the Company’s forward foreign exchange contracts were denominated in Indonesian rupiah, Czech koruna, and Colombian peso. At September 30, 2022, the Company’s forward foreign exchange contracts were denominated in Indonesian rupiah and Czech koruna. Accounting for Derivative Instruments and Hedging Activities Net Investment Hedge For net investment hedges, changes in the fair value of the effective portion of the derivatives’ gains or losses are reported as CTA in AOCI while changes in the ineffective portion are reported in earnings. Effectiveness is assessed based on the hypothetical derivative method. The gains or losses on derivative instruments reported in AOCI are reclassified to earnings in the period in which earnings are affected by the underlying item, such as a disposal or substantial liquidations of the entities being hedged. Cash settlements related to the net investment hedge 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. During fiscal 2023, 2022 and 2021 the Company received net cash interest of $ 4 million, $ 4 million and $ 3 million, respectively. As of September 30, 2023 and 2022, the fair value of these swaps was an asset of $ 12 million and $ 29 million, respectively, was included in Prepaid expenses and other current assets and Other assets, and the cumulative unrealized gain of $ 15 million and $ 32 million, respectively, 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: Years Ended September 30 2023 2022 2021 2023 2022 2021 2023 2022 2021 Description Gain/(Loss) Recognized in AOCI (Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated (Gain)/Loss Recognized in Interest (In millions) Cross-currency swaps $ ( 13 ) $ 30 $ 7 $ ( 6 ) $ ( 6 ) $ ( 5 ) $ 2 $ 2 $ 2 Forward Foreign Currency Contracts At both September 30, 2023 and 2022, the Company had foreign currency forward contracts that were not designated as hedges for accounting purposes. 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 September 30, 2023 and 2022, the fair value of derivative instruments not designated as hedges wa s less than $ 1 million and was presented in Accounts payable and accrued liabilities on the Consolidated Balance Sheets.

Insurance Recoveries

Insurance Recoveries	12 Months Ended
	Sep. 30, 2023
Insurance Recovery [Abstract]
Insurance Recoveries	Note L. Insurance Recoveries Pepinster, Belgium In July 2021, the Company’s Specialty Compounds manufacturing and research and development facility in Pepinster, Belgium experienced significant flooding. Full production, which was temporarily halted, resumed in the second quarter of fiscal 2022. The Company agreed to a final insurance settlement in fiscal 2023 for total proceeds of $ 33 million. During fiscal 2023, 2022 and 2021, the Company recorded expenses of nil , $ 6 million and $ 17 million for clean-up costs, inventory, and fixed asset impairments and simultaneously recognized a fully offsetting loss recovery from expected insurance proceeds. During fiscal 2023, the Company recognized gains of $ 9 million related to lost margin and the replacement value of fixed assets exceeding their net book value. The flood-related expenses, loss recoveries and gains are included within Cost of sales in the Consolidated Statements of Operations in fiscal 2023, 2022 and 2021. During fiscal 2023, 2022 and 2021, the Company received insurance proceeds of $ 14 million, $ 11 million and $ 8 million, respectively. Of the proceeds received, $ 12 million, $ 1 million and $ 2 million, is included in Cash provided by investing activities and $ 2 million, $ 10 million and $ 6 million, is included in Cash provided by operating activities for fiscal 2023, 2022 and 2021, respectively, in the Consolidated Statements of Cash Flows. Franklin, Louisiana In August 2021, the Company’s specialty carbons and reinforcing carbons manufacturing facility in Franklin, Louisiana experienced an unplanned plant outage due to equipment failure. During fiscal 2022, the Company received insurance proceeds of $ 8 million for business interruption. These proceeds were included within Cost of sales in the Consolidated Statements of Operations and in Cash Provided by operating activities in the Consolidated Statements of Cash Flows for the fiscal year ended September 30, 2022.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Employee Benefit Plans	Note M. Employee Benefit Plans The information below provides detail concerning the Company’s benefit obligations under the defined benefit and postretirement benefit plans it sponsors. Defined benefit plans provide pre-determined benefits to employees that are distributed upon retirement. Cabot is making all sponsor required contributions to these plans. The accumulated benefit obligation was $ 2 million for the U.S. defined benefit plan and $ 131 million for the foreign defined benefit plans as of September 30, 2023 and $ 2 million for the U.S. defined benefit plans and $ 125 million for the foreign defined benefit plans as of September 30, 2022. The U.S. defined benefit plan is the frozen Supplemental Cash Balance Plan. The following provides information about projected benefit obligations, plan assets, the funded status and weighted-average assumptions of the defined benefit pension and postretirement benefit plans: Years Ended September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Change in Benefit Obligations: Benefit obligation at beginning of $ 2 $ 133 $ 3 $ 221 $ 16 $ 13 $ 25 $ 19 Service cost — 3 — 4 — — — — Interest cost — 7 — 4 1 1 — 1 Plan participants’ contribution — 1 — 1 — — — — Foreign currency exchange rate — 6 — ( 27 ) — 1 — ( 2 ) (Gain) loss from changes in actuarial — ( 4 ) ( 1 ) ( 43 ) ( 1 ) ( 3 ) ( 4 ) ( 5 ) Benefits paid — ( 5 ) — ( 9 ) ( 2 ) ( 1 ) ( 3 ) — Settlem ents or curtailments — ( 2 ) — ( 2 ) — — ( 2 ) — Divestiture of a business — — — ( 16 ) — — — — Benefit obligation at end of year $ 2 $ 139 $ 2 $ 133 $ 14 $ 11 $ 16 $ 13 Years Ended September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Change in Plan Assets: Fair value of plan assets at beginning $ — $ 135 $ — $ 217 $ — $ — $ — $ — Actual return on plan assets — 4 — ( 35 ) — — — — Employer contribution — 4 — 5 2 1 5 — Plan participants’ contribution — 1 — 1 — — — — Foreign currency exchange rate — 7 — ( 24 ) — — — — Benefits paid — ( 5 ) — ( 9 ) ( 2 ) ( 1 ) ( 3 ) — Settlements or curtailments — ( 2 ) — ( 2 ) — — ( 2 ) — Expenses paid from assets — — — — — — — — Divestiture of a business — — — ( 18 ) — — — — Fair value of plan assets at end $ — $ 144 $ — $ 135 $ — $ — $ — $ — Funded status $ ( 2 ) $ 5 $ ( 2 ) $ 2 $ ( 14 ) $ ( 11 ) $ ( 16 ) $ ( 13 ) Recognized asset (liability) $ ( 2 ) $ 5 $ ( 2 ) $ 2 $ ( 14 ) $ ( 11 ) $ ( 16 ) $ ( 13 ) Pension Assumptions and Strategy The following assumptions were used to determine the pension benefit obligations and periodic benefit costs as of and for the years ended September 30: 2023 2022 2021 Pension Benefits U.S. Foreign U.S. Foreign U.S. Foreign Actuarial assumptions as of the year-end Discount rate 6.0 % 4.7 % 5.5 % 4.5 % 2.2 % 2.1 % Rate of increase in compensation N/A 3.0 % 3.0 % 3.0 % N/A 2.9 % Cash balance interest credit rate 2.0 % 2.1 % 2.0 % 2.0 % 2.0 % 1.7 % Actuarial assumptions used to determine net Discount rate - benefit obligation 5.6 % 4.5 % 2.2 % 2.1 % 2.5 % 1.7 % Discount rate - service cost N/A 3.6 % N/A 2.0 % N/A 1.7 % Discount rate - interest cost 5.3 % 4.5 % 1.6 % 1.7 % 1.4 % 1.4 % Expected long-term rate of return on N/A 5.1 % N/A 3.5 % N/A 4.6 % Rate of increase in compensation N/A 3.0 % N/A 2.9 % N/A 3.0 % Cash balance interest credit rate 2.0 % 2.0 % 2.0 % 1.7 % 2.1 % 1.7 % Postretirement Assumptions and Strategy The following assumptions were used to determine the postretirement benefit obligations and net costs as of and for the years ended September 30: 2023 2022 2021 Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign Actuarial assumptions as of the year-end Discount rate 6.0 % 5.7 % 5.6 % 5.1 % 2.4 % 2.8 % Initial health care cost trend rate (1) 5.0 % 6.4 % — % 6.8 % 5.5 % 6.9 % Actuarial assumptions used to determine Discount rate - benefit obligation 5.6 % 5.1 % 2.4 % 2.8 % 2.1 % 2.4 % Discount rate - service cost 5.4 % 5.1 % 1.7 % 3.5 % 1.5 % 3.0 % Discount rate - interest cost 5.3 % 5.1 % 1.6 % 2.5 % 1.4 % 2.1 % Initial health care cost trend rate (1) — % 6.8 % 5.5 % 6.9 % 6.0 % 6.9 % (1) The initial health care cost trend rate is set at 5 % for the 2023 U.S. plan assumptions as the 2024 Medicare Part B premiums are expected to increase. The trend rates for all future years beyond 2024 also reflect expected 5 % increases. The initial health care cost trend rate was set at zero for the 2022 U.S. plan assumptions in light of the expected downward adjustment the U.S. government was expected to make to the 2023 Medicare Part B premiums, however, all trend rates beyond the initial year were set to 5 % . Cabot uses discount rates as of September 30, the plans’ measurement date, to determine future benefit obligations under its U.S. and foreign defined benefit plans. The discount rates for the defined benefit plans in Canada, the Eurozone, Japan, Switzerland, the United Arab Emirates, the United Kingdom and the U.S. are derived from yield curves that reflect high quality corporate bond yield or swap rate information in each region and reflect the characteristics of Cabot’s employee benefit plans. The discount rates for the defined benefit plans in Mexico, the Czech Republic and Indonesia are based on government bond indices that best reflect the durations of the plans, adjusted for credit spreads presented in selected AA corporate bond indices. The rates utilized are selected because they represent long-term, high quality, fixed income benchmarks that approximate the long-term nature of Cabot’s pension obligations and related payouts. Amounts recognized in the Consolidated Balance Sheets at September 30, 2023 and 2022 related to the Company's defined benefit pension and postretirement benefit plans were as follows: September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Other assets $ — $ 30 $ — $ 26 $ — $ — $ — $ — Accounts payable and accrued liabilities $ — $ ( 1 ) $ — $ ( 1 ) $ ( 2 ) $ ( 1 ) $ ( 2 ) $ ( 1 ) Other liabilities $ ( 2 ) $ ( 24 ) $ ( 2 ) $ ( 23 ) $ ( 12 ) $ ( 10 ) $ ( 14 ) $ ( 12 ) Amounts recognized in AOCI at September 30, 2023 and 2022 related to the Company's defined benefit pension and postretirement benefit plans were as follows: September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Net actuarial (gain) loss $ — $ 24 $ — $ 23 $ ( 6 ) $ ( 7 ) $ ( 6 ) $ ( 4 ) Net prior service credit — ( 1 ) — ( 1 ) — — — — Balance in accumulated other $ — $ 23 $ — $ 22 $ ( 6 ) $ ( 7 ) $ ( 6 ) $ ( 4 ) Estimated Future Benefit Payments The Company expects that the following benefit payments will be made to plan participants in the years from 2024 to 2033: Pension Benefits Postretirement Benefits Years Ending September 30 U.S. Foreign U.S. Foreign (In millions) 2024 $ — $ 9 $ 2 $ 1 2025 $ — $ 9 $ 2 $ 1 2026 $ — $ 9 $ 2 $ 1 2027 $ — $ 11 $ 2 $ 1 2028 $ — $ 11 $ 2 $ 1 2029 - 2033 $ 1 $ 49 $ 6 $ 4 Postretirement medical benefits are unfunded and impact Cabot’s cash flows as benefits become due, which is expected to be $ 3 million in fiscal 2024. The Company expects to contribute $ 4 million to its pension plans in fiscal 2024. Net periodic defined benefit pension and other postretirement benefit costs include the following components: Years Ended September 30 2023 2022 2021 2023 2022 2021 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Service cost $ — $ 3 $ — $ 4 $ — $ 6 $ — $ — $ — $ — $ — $ — Interest cost — 7 — 4 — 3 1 1 — 1 — 1 E xpected return on plan — ( 7 ) — ( 6 ) — ( 10 ) — — — — — — A mortizatio n of n et l osses — ( 1 ) — 1 — 3 ( 1 ) — — — — — Settlements or — — — — 4 1 — — ( 1 ) — — — Other — — — — — 2 — — — — — — Net periodic (benefit) cost $ — $ 2 $ — $ 3 $ 4 $ 5 $ — $ 1 $ ( 1 ) $ 1 $ — $ 1 Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss) are as follows: Years Ended September 30 2023 2022 2021 2023 2022 2021 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Net (gains) losses $ — $ 1 $ — $ ( 2 ) $ ( 2 ) $ ( 15 ) $ ( 1 ) $ ( 3 ) $ ( 4 ) $ ( 4 ) $ — $ ( 2 ) Prior service (credit) cost — — — — — ( 1 ) — — — — — Amortization of prior — 1 — ( 1 ) — ( 3 ) 1 — — — — — Loss on divestiture — — — ( 2 ) — — — — — — — — (Loss) g ain on settl ements — — — — ( 4 ) ( 1 ) — — 1 — — — Net changes recognized in (1) $ — $ 2 $ — $ ( 5 ) $ ( 6 ) $ ( 20 ) $ — $ ( 3 ) $ ( 3 ) $ ( 4 ) $ — $ ( 2 ) (1) The tax impact on pension and other postretirement benefit liability adjustments arising during the period was a tax provision of less than $ 1 million, a tax benefit of $ 3 million and a tax benefit of $ 8 million for fiscal 2023, 2022 and 2021, respectively. U.K. Plans Termination In fiscal 2023, the Company commenced the plan termination process for the Cabot Carbon Limited Pension Plan and Carbon Plastics Pension Plan and expects to complete the transaction in fiscal 2024. Plan Assets The Company’s foreign defined benefit pension plans weighted-average asset allocations at September 30, 2023 and 2022 by asset category, are as follows: September 30 2023 2022 Equity securities 19 % 20 % Debt securities 31 % 68 % Real estate 10 % 7 % Cash and other securities (1) 40 % 5 % Total 100 % 100 % (1) The asset allocation is temporarily changed as a result of the insurance contracts Cabot Carbon Limited Pension Plan and Carbon Plastics Pension Plan purchased with plan assets in anticipation of the settlement discussed above. To develop the expected long-term rate of return on plan assets assumption, the Company used a capital asset pricing model. The model considers the current level of expected returns on risk-free investments comprised of government bonds, the historical level of the risk premium associated with the other asset classes in which the portfolio is invested and the expectations for future returns for each asset class. The expected return for each asset class was then weighted based on the target asset allocation to develop the expected long-term rate of return for each plan. Cabot’s investment strategy for each of its foreign defined benefit plans is generally based on a set of investment objectives and policies that cover time horizons and risk tolerance levels consistent with plan liabilities. Periodic studies are performed to determine the asset mix that will meet pension obligations at a reasonable cost to the Company. The assets of the defined benefit plans are comprised principally of investments in equity and high-quality fixed income securities, which are broadly diversified across the capitalization and style spectrum and are managed using both active and passive strategies. The weighted average target asset allocation for the foreign plans is 29 % in equity, 46 % in fixed income, 18 % in real estate and 7 % in cash and other securities. For pension plan assets classified as Level 1 measurements (measured using quoted prices in active markets), total fair value is either the price of the most recent trade at the time of the market close or the official close price, as defined by the exchange on which the asset is most actively traded on the last trading day of the period, multiplied by the number of units held without consideration of transaction costs. For pension plan assets classified as Level 2 measurements, where the security is frequently traded in less active markets, fair value is based on the closing price at the end of the period; where the security is less frequently traded, fair value is based on the price a dealer would pay for the security or similar securities, adjusted for any terms specific to that asset or liability. Market inputs are obtained from third-party vendors of market data and subjected to tolerance/quality checks. The fair value of the Company’s pension plan assets at September 30, 2023 and 2022 by asset category is as follows: September 30 2023 2022 Quoted Prices in Significant Total Quoted Prices in Significant Total (In millions) Cash $ — $ — $ — $ 1 $ — $ 1 Direct investments: U.S government bonds — — — — — — U.S. corporate bonds — — — — — — Non-U.S. equities 6 — 6 4 — 4 Non-U.S. government bonds 2 — 2 1 — 1 Non-U.S. corporate bonds 3 — 3 2 — 2 Mortgage-backed securities — 1 1 — 1 1 Other fixed income 1 — 1 1 — 1 Total direct investments 12 1 13 8 1 9 Investment funds: Equity funds (1) — 21 21 — 23 23 Fixed income funds (2) — 38 38 — 86 86 Real estate funds (3) — 15 15 — 9 9 Cash equivalent funds 4 — 4 1 — 1 Other investment funds — — — — 1 1 Total investment funds 4 74 78 1 119 120 Alternative investments: Insurance contracts (4) — 52 52 — 5 5 Other alternative investments — 1 1 — — — Total alternative investments — 53 53 — 5 5 Total pension plan assets $ 16 $ 128 $ 144 $ 10 $ 125 $ 135 (1) The equity funds asset class includes funds that invest in U.S. equities as well as equity securities issued by companies incorporated, listed or domiciled in countries in developed and/or emerging markets. These companies may be in the small-, mid- or large-cap categories. (2) The fixed income funds asset class includes investments in high quality funds. High quality fixed income funds primarily invest in low-risk U.S. and non-U.S. government securities, investment-grade corporate bonds, mortgages and asset-backed securities. A significant portion of the fixed income funds include investment in long-term bond funds. (3) The real estate funds asset class includes funds that primarily invest in entities which are principally engaged in the ownership, acquisition, development, financing, sale and/or management of income-producing real estate properties, both commercial and residential. These funds typically seek long-term growth of capital and current income that is above average relative to public equity funds. (4) Insurance contracts held by the Company’s non-U.S. plans are issued by well-known, highly rated insurance companies. Defined Contribution Plans In addition to benefits provided under the defined benefit and postretirement benefit plans, the Company provides benefits under defined contribution plans. Cabot recognized expenses related to these plans of $ 19 million, $ 15 million and $ 18 million in fiscal 2023, 2022 and 2021, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Note N. Stock-Based Compensation The Cabot Corporation Amended and Restated 2017 Long-Term Incentive Plan (the “Amended Plan”) was established by the Company to provide stock-based compensation to eligible employees. The Amended Plan was approved by Cabot’s stockholders on March 11, 2021 and authorizes the issuance of up to 8,625,000 shares of common stock. It is the only equity incentive plan under which the Company may grant equity awards to employees. The terms of awards made under Cabot’s equity compensation plans are generally determined by the Compensation Committee of Cabot’s Board of Directors. The awards made in fiscal 2023, 2022 and 2021 consist of grants of stock options, time-based restricted stock units and performance-based restricted stock units. The options were issued with an exercise price equal to 100 % of the market price of Cabot’s common stock on the date of grant, generally vest over a three-year period ( 30 % on each of the first and second anniversaries of the date of grant and 40 % on the third anniversary of the date of grant) and have a ten-year term. The restricted stock units generally vest three years from the date of the grant. The number of shares issuable, if any, when a performance-based restricted stock unit award vests will depend on the degree of achievement of the corporate performance metrics for each year within the three-year performance period of the award. Accordingly, future compensation costs associated with outstanding awards of performance-based restricted stock units may increase or decrease based on the probability of the Company achieving the performance metrics. Stock-based employee compensation expense was $ 18 million, $ 22 million and $ 20 million, after tax, for fiscal 2023, 2022 and 2021, respectively. The following table presents stock-based compensation expenses included in the Company’s Consolidated Statements of Operations: Years Ended September 30 2023 2022 2021 (In millions) Cost of sales $ 2 $ 3 $ 2 Selling and administrative expenses 16 18 17 Research and technical expenses 2 2 2 Stock-based compensation expense 20 23 21 Income tax benefit ( 2 ) ( 1 ) ( 1 ) Net stock-based compensation expense $ 18 $ 22 $ 20 As of September 30, 2023, Cabot had $ 16 million and $ 3 million of total unrecognized compensation cost related to restricted stock units and options, respectively, granted under the Company’s equity incentive plans. These costs are expected to be recognized over a weighted-average period of approximately one year for restricted stock units and options. Equity Incentive Plan Activity The following table summarizes the total stock option and restricted stock unit activity in the equity incentive plans for fiscal 2023: Stock Options Restricted Stock Units Total (1) Weighted Restricted (4) Weighted (Shares in thousands) Outstanding at September 30, 2022 1,574 $ 49.89 1,012 $ 48.95 Granted 157 $ 73.84 225 $ 73.68 Performance-based adjustment (2) — $ — $ 20 $ 51.88 Exercised / Vested ( 75 ) $ 47.77 ( 275 ) $ 50.43 Cancelled / Forfeited ( 15 ) $ 49.88 ( 44 ) $ 50.20 Outstanding at September 30, 2023 (3) 1,641 $ 52.27 938 $ 54.45 Exercisable at September 30, 2023 1,172 $ 50.02 (1) Unvested stock options were approximately 469,000 a nd 651,000 at September 30, 2023 and 2022 and their weighted average grant date fair values were $ 57.92 and $ 49.30 , respectively. (2) Represents the net incremental number of shares issuable upon vesting of performance-based restricted stock units based on the Company’s actual financial performance metrics for fiscal 2023. (3) Stock options outstanding include options vested and expected to vest in the future and have a weighted average remaining contractual life of 6.13 years. (4) The number granted represents the number of shares issuable upon vesting of time-based restricted stock units and performance-based restricted stock units, assuming the Company performs at the target performance level in each year of the three-year performance period. Stock Options As of September 30, 2023, the aggregate intrinsic value for all options outstanding and options exercisable was $ 29 million. The intrinsic value of options exercised during fiscal 2023, 2022 and 2021 was $ 2 million, $ 4 million and $ 2 million, respectively, and the Company received cash of $ 4 million, $ 6 million and $ 5 million, respectively, from these exercises. The Company recognized immaterial tax benefits in fiscal 2023, 2022 and 2021 from the exercise of stock options which were included in (Provision) benefit for income taxes within the Consolidated Statements of Operations. The Company uses the Black-Scholes option-pricing model to estimate the fair value of the options at the grant date. The weighted average grant date fair values of options granted during fiscal 2023, 2022 and 2021 was $ 26.28 , $ 15.95 , and $ 9.69 per option, respectively. The fair values on the grant date were calculated using the following weighted-average assumptions: Years Ended September 30 2023 2022 2021 Expected stock price volatility 38 % 35 % 36 % Risk free interest rate 4.0 % 1.4 % 0.6 % Expected life of options (years) 6 6 6 Expected annual dividends per year $ 1.48 $ 1.40 $ 1.40 The expected stock price volatility assumption was determined using the historical volatility of the Company’s common stock over the expected life of the option. The expected term reflects the anticipated time period between the measurement date and the exercise date or post-vesting cancellation date. Restricted Stock Units The value of restricted stock unit awards is the closing stock price at the date of the grant. The weighted average grant date fair values of restricted stock unit awards granted during fiscal 2023, 2022 and 2021 was $ 73.68 , $ 58.72 and $ 41.92 , respectively. The intrinsic value of restricted stock units (meaning the fair value of the units on the date of vesting) that vested during fiscal 2023, 2022 and 2021 was $ 20 million, $ 13 million and $ 8 million, respectively. Supplemental 401(k) Plan Cabot’s Deferred Compensation and Supplemental Retirement Plan (“SERP 401(k)”) provides benefits to highly compensated employees when the retirement plan limits established under the Internal Revenue Code prevent them from receiving all of the Company matching and retirement contributions that would otherwise be provided under the qualified 401(k) plan. The SERP 401(k) is non-qualified and unfunded. Contributions under the SERP 401(k) are treated as if invested in Cabot common stock. The majority of the distributions made under the SERP 401(k) are required to be paid with shares of Cabot common stock. The remaining distributions, which relate to certain grandfathered accounts, will be paid in cash based on the market price of Cabot common stock at the time of distribution. The aggregate value of the accounts that will be paid out in stock, which is equivalent to approximately 113,000 and 103,000 shares of Cabot common stock as of September 30, 2023 and 2022, respectively, is reflected at historic cost in stockholders’ equity, and the aggregate value of the accounts that will be paid in cash, which was immaterial as of September 30, 2023 and 2022, was included in Other liabilities and marked-to-market quarterly.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Sep. 30, 2023
Stockholders' Equity Note [Abstract]
Accumulated Other Comprehensive Income (Loss)	Note O. Accumulated Other Comprehensive Income (Loss) Changes in each component of AOCI, net of tax, are as follows for fiscal 2023 and 2022: Currency Pension and Other Total (In millions) Balance at September 30, 2021 attributable to $ ( 265 ) $ ( 24 ) $ ( 289 ) Other comprehensive income (loss) before reclassifications ( 208 ) 12 ( 196 ) Amounts reclassified from AOCI 29 2 31 Less: Other comprehensive income (loss) attributable to ( 15 ) — ( 15 ) Balance at September 30, 2022 attributable to ( 429 ) ( 10 ) ( 439 ) Other comprehensive income (loss) before reclassifications 80 3 83 Amounts reclassified from AOCI ( 4 ) ( 2 ) ( 6 ) Less: Other comprehensive income (loss) attributable to — — — Balance at September 30, 2023 attributable to $ ( 353 ) $ ( 9 ) $ ( 362 ) The amounts reclassified out of AOCI and into the Consolidated Statements of Operations for fiscal 2023, 2022 and 2021 are as follows: Affected Line Item in the Consolidated Years Ended September 30 Statements of Operations 2023 2022 2021 (In Millions) Derivatives: net investment hedges (Gains) losses reclassified to interest Interest expense $ ( 6 ) $ ( 6 ) $ ( 5 ) (Gains) losses excluded from effectiveness Interest expense 2 2 2 Release of current translation adjustment Loss on sale of business and asset impairment charge — 33 — Pension and other postretirement benefit Release of actuarial losses and prior service cost Loss on sale of business and asset impairment charge — 2 — Amortization of actuarial losses and prior service Other income (expense) ( 2 ) 1 3 Settlement and curtailment loss (gain) Other income (expense) — ( 1 ) 5 Total before tax $ ( 6 ) $ 31 $ 5

Earnings Per Share

Earnings Per Share	12 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings Per Share	Note P. Earnings Per Share The following tables summarize the components of the basic and diluted earnings per common share (“EPS”) computations: Years Ended September 30 2023 2022 2021 (In millions, except per share amounts) Basic EPS: Net income (loss) attributable to Cabot Corporation $ 445 $ 209 $ 250 Less: Dividends and dividend equivalents to participating 1 1 1 Less: Undistributed earnings allocated to participating (1) 7 2 2 Earnings (loss) allocated to common shareholders (numerator) $ 437 $ 206 $ 247 Weighted average common shares and participating 57.3 57.4 57.5 Less: Participating securities (1) 1.2 0.9 0.8 Adjusted weighted average common shares 56.1 56.5 56.7 Per share amounts—basic: Net income (loss) attributable to Cabot Corporation $ 7.79 $ 3.65 $ 4.35 Diluted EPS: Earnings (loss) allocated to common shareholders $ 437 $ 206 $ 247 Plus: Earnings allocated to participating securities 8 3 3 Less: Adjusted earnings allocated to participating (2) 8 3 3 Earnings (loss) available to common shares (numerator) $ 437 $ 206 $ 247 Adjusted weighted average common shares outstanding 56.1 56.5 56.7 Effect of dilutive securities: Common shares issuable (3) 0.4 0.4 0.1 Adjusted weighted average common shares 56.5 56.9 56.8 Per share amounts—diluted: Net income (loss) attributable to Cabot Corporation $ 7.73 $ 3.62 $ 4.34 (1) Participating securities consist of shares underlying unvested time-based restricted stock units (the "TSUs"), earned and unvested performance-based restricted stock units (the "PSUs", and referred to in this note collectively with the TSUs as the "RSUs"), stock units accounted for under the Supplemental 401(k) Plan portion of the Company’s Deferred Compensation and Supplemental Retirement Plan, and stock units and phantom stock units accounted for under the Company’s Non-Employee Directors’ Deferral Plan. The holders of RSUs are entitled to receive dividend equivalents, payable in cash, to the extent dividends are paid on the outstanding shares of Common Stock, and equal in value to the dividends that would have been paid in respect of the Common Stock underlying the RSU. The accounts of holders of stock units and phantom stock units are credited with dividend equivalents, which are payable, in stock or cash, as the case may be, with the distribution of account balances . 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: Years Ended September 30 2023 2022 2021 (In millions) Calculation of undistributed earnings: Net income (loss) attributable to Cabot Corporation $ 445 $ 209 $ 250 Less: Dividends declared on common stock 87 84 80 Less: Dividends and dividend equivalents to participating 1 1 1 Undistributed earnings (loss) $ 357 $ 124 $ 169 Allocation of undistributed earnings: Undistributed earnings (loss) allocated to common $ 350 $ 122 $ 167 Undistributed earnings allocated to participating 7 2 2 Undistributed earnings (loss) $ 357 $ 124 $ 169 (2) Undistributed earnings (loss) are adjusted for the assumed conversion of dilutive securities, which are described in (3) below, to common shares and then reallocated to participating securities. (3) Represents incremental shares of common stock from the assumed exercise of stock options issued under Cabot’s equity incentive plans. For fiscal 2023, 2022 and 2021, respectively, 138,966 , 214,180 and 525,131 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.

Income Taxes

Income Taxes	12 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Note Q. Income Taxes Income from operations before income taxes and equity in net earnings of affiliated companies was as follows: Years Ended September 30 2023 2022 2021 (In millions) Domestic $ 65 $ ( 20 ) $ ( 73 ) Foreign 386 355 479 Income from operations before income taxes and $ 451 $ 335 $ 406 Tax provision (benefit) for income taxes consisted of the following: Years Ended September 30 2023 2022 2021 (In millions) U.S. federal and state: Current $ 5 $ 7 $ 11 Deferred ( 156 ) 2 ( 1 ) Total ( 151 ) 9 10 Foreign: Current 123 135 103 Deferred — ( 42 ) 10 Total 123 93 113 Provision (benefit) for income taxes $ ( 28 ) $ 102 $ 123 The provision ( benefit ) for income taxes differed from the provision for income taxes as calculated using the U.S. statutory rate as follows: Years Ended September 30 2023 2022 2021 (In millions) Computed tax expense at the federal statutory rate $ 95 $ 70 $ 85 Foreign impact of taxation at different rates, repatriation, 30 38 8 Global Intangible Low Taxed Income (GILTI) 15 23 18 Purification Solutions business divestiture — ( 179 ) — Impact of the Coronavirus Aid, Relief, and Economic — — 10 Impact of increase (decrease) in valuation allowance on ( 156 ) 160 ( 1 ) U.S. and state benefits from research and experimentation ( 2 ) ( 2 ) ( 2 ) Provision (settlement) of unrecognized tax benefits 2 1 1 Permanent differences, net ( 4 ) 10 7 State taxes, net of federal effect ( 8 ) ( 19 ) ( 3 ) Provision (benefit) for income taxes $ ( 28 ) $ 102 $ 123 Significant components of deferred income taxes were as follows: September 30 2023 2022 (In millions) Deferred tax assets: Deferred expenses $ 50 $ 10 Intangible assets 42 39 Inventory 14 15 Operating lease liability 22 21 Other 6 32 U.S. federal interest expense carryforward 42 33 Pension and other benefits 24 29 Net operating loss carryforwards 244 224 Capital loss carryforwards 132 137 Foreign tax credit carryforwards 68 55 R&D credit carryforwards 49 47 Other business credit carryforwards 19 20 Subtotal 712 662 Valuation allowance ( 498 ) ( 580 ) Total deferred tax assets $ 214 $ 82 September 30 2023 2022 (In millions) Deferred tax liabilities: Property, plant and equipment $ ( 47 ) $ ( 59 ) Right of use asset ( 22 ) ( 21 ) Unremitted earnings of non-U.S. subsidiaries ( 15 ) ( 22 ) Total deferred tax liabilities $ ( 84 ) $ ( 102 ) The Company assesses the available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit utilization of the existing deferred tax assets. When performing this assessment, the Company looks to the potential future reversal of existing taxable temporary differences, taxable income in carryback years and the feasibility of tax planning strategies and estimated future taxable income. Failure to achieve operating income targets resulting in a cumulative loss may change the Company’s assessment regarding the realization of Cabot’s deferred tax assets, resulting in valuation allowance being recorded against some or all of the Company’s deferred tax assets. The need for a valuation allowance can also be affected by changes to tax laws, changes to statutory tax rates and changes to future taxable income estimates. A valuation allowance represents management’s best estimate of the non-realizable portion of the deferred tax assets. Any adjustments in a valuation allowance would result in an adjustment to income tax expense. Since 2020, the Company has maintained a valuation allowance against its net U.S. deferred tax assets. On a quarterly basis, the Company evaluates all positive and negative evidence to determine if a valuation allowance is required. In analyzing all available evidence as of September 30, 2023, the Company determined that there is sufficient positive evidence outweighing the negative evidence to conclude that it is more likely than not that a portion of the U.S. deferred tax assets are realizable. As a result, the Company reversed a portion of the valuation allowance that was recorded against U.S. net deferred tax assets. This reversal resulted in a non-cash income tax benefit of $ 152 million. The Company continues to maintain a valuation allowance in the U.S. against capital losses, interest expense limitation carryforwards, certain foreign tax credits, certain R&D tax credits, and certain state deferred tax assets that the Company does not expect to realize. The valuation allowance decreased by $ 82 million from $ 580 million in fiscal 2022 compared to $ 498 million in fiscal 2023, primarily due to the reversal of a portion of the valuation allowance on the ending U.S. net deferred tax assets, which was partially offset by an increase in valuation allowance on current year activity of U.S. deferred tax assets and an increase in valuation allowance on foreign deferred tax assets on some of the Company's net operating losses. The valuation allowance increased by $ 110 million from $ 470 million in fiscal 2021 compared to $ 580 million in fiscal 2022, primarily due to the tax loss related to the divestiture of the Purification Solutions business. After the valuation allowance, approximately $ 24 million of foreign NOLs and less than $ 1 million of other tax credit carryforwards remained at September 30, 2023. The benefits of these carryforwards are dependent upon taxable income during the carryforward period in the jurisdictions in which they arose. The following table provides detail surrounding the expiration dates of NOLs, capital loss and other tax credit carryforwards before valuation allowances: Years Ending September 30 NOLs/Capital Losses Credits (In millions) 2024 - 2030 $ 1,051 $ 31 2031 and thereafter 268 103 Indefinite carryforwards 793 2 Total $ 2,112 $ 136 As of September 30, 2023, provisions have not been made for non-U.S. withholding taxes or other applicable taxes on $ 1,359 million of undistributed earnings of non-U.S. subsidiaries, as these earnings are considered indefinitely reinvested. It is not practicable to calculate the unrecognized deferred tax liability on undistributed earnings. Cabot continually reviews the financial position and forecasted cash flows of its U.S. consolidated group and foreign subsidiaries in order to reaffirm the Company’s intent and ability to continue to indefinitely reinvest earnings of its foreign subsidiaries or whether such earnings will need to be repatriated in the foreseeable future. Such review encompasses operational needs and future capital investments. From time to time, however, the Company’s intentions relative to specific indefinitely reinvested amounts change because of certain unique circumstances. These earnings could become subject to non-U.S. withholding taxes and other applicable taxes if they were remitted to the U.S. Cabot has filed its tax returns in accordance with the tax laws in each jurisdiction and recognizes tax benefits for uncertain tax positions when the position would more likely than not be sustained based on its technical merits and recognizes measurement adjustments when needed. As of September 30, 2023, the total amount of unrecognized tax benefits was $ 20 million, of which $ 6 million was recorded in Other liabilities in the Consolidated Balance Sheet and, $ 14 million was offset against deferred tax assets. In 2022, we reported an uncertain tax position of $ 137 million related to the initially anticipated filing position on the character of a portion of the tax loss from Purification Solutions business divestiture. Upon completion of the U.S. Consolidated tax return in 2023, the Company has reversed the $ 137 million unrecognized tax benefit which reflects the final position ultimately taken on the filed tax return. In addition, accruals of $ 5 million have been recorded for penalties and interest, as of September 30, 2023. Total penalties and interest recorded in the tax provision in the Consolidated Statements of Operations was $ 2 million in fiscal 2023, $ 2 million in fiscal 2022 and $ 1 million in fiscal 2021. If the unrecognized tax benefits were recognized as of September 30, 2023, there would be $ 20 million favorable impact on the Company’s tax provision before consideration of the impact of the potential need for valuation allowances. A reconciliation of the beginning and ending amount of unrecognized tax benefits for fiscal 2023, 2022 and 2021 is as follows: Years Ended September 30 2023 2022 2021 (In millions) Balance at beginning of the year $ 159 $ 21 $ 23 Additions based on tax positions related to the current 1 138 1 Additions for tax positions of prior years — 2 — Reductions of tax positions of prior years ( 137 ) ( 1 ) ( 2 ) Reductions related to settlements ( 2 ) — — Reductions from lapse of statute of limitations ( 1 ) ( 1 ) ( 1 ) Balance at end of the year $ 20 $ 159 $ 21 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 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 is subject to taxation in the United States and various states and foreign jurisdictions. The 2020 through 2022 tax years generally remain subject to examination by the IRS and various tax years from 2010 through 2022 remain subject to examination by the respective state tax authorities. In foreign jurisdictions, various tax years from 2006 through 2022 remain subject to examination by their respective tax authorities.

Leases

Leases	12 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Leases	Note R. 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. A right of use (“ROU”) asset is recorded and recognized at commencement at the lease liability amount, adjusted for lease prepayments, initial direct costs incurred and lease incentives received. The Company’s lease terms 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 sixteen 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-nine years . 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: Years Ended September 30 2023 2022 2021 (In millions) Operating lease cost $ 26 $ 23 $ 25 Finance lease cost 6 6 7 Total lease cost $ 32 $ 29 $ 32 Included within operating lease costs are short-term lease costs, which were $ 7 million in fiscal 2023 and $ 5 million in both fiscal 2022 and 2021. Some lease arrangements require variable payments that are dependent on usage, output, or index-based adjustments. Variable lease costs wer e $ 2 million in fiscal 2023 and $ 1 million in both 2022 and 2021. Supplemental cash flow information related to the Company’s leases was as follows: Years Ended September 30 2023 2022 2021 (In millions) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 18 $ 17 $ 20 Operating cash flows from finance leases 2 2 2 Financing cash flows from finance leases 3 4 3 Right-of-use assets obtained in exchange for new operating lease liabilities $ 11 $ 14 $ 6 Right-of-use assets obtained in exchange for new finance lease liabilities $ 4 $ 1 $ 4 Supplemental balance sheet information related to the Company’s leases was as follows: Description Balance Sheet Classification September 30, 2023 September 30, 2022 (In millions) Lease ROU assets: Operating Other assets $ 101 $ 96 Finance Net property, plant and equipment 39 41 Total lease ROU assets $ 140 $ 137 Lease liabilities: Current: Operating Accounts payable and accrued liabilities $ 15 $ 14 Finance Current portion of long-term debt 4 3 Long-term: Operating Other liabilities 84 83 Finance Long-term debt 24 26 Total lease liabilities $ 127 $ 126 The following table presents the weighted-average remaining lease term and discount rates for the Company’s leases: Description September 30, 2023 September 30, 2022 Weighted-average remaining lease term (years): Operating leases 15 15 Finance leases 9 10 Weighted-average discount rate: Operating leases 3.28 % 2.97 % Finance leases 5.38 % 5.40 % Future minimum lease payments under non-cancelable operating and finance leases as of September 30, 2023 were as follows: Years Ended September 30 Operating leases Finance leases (In millions) 2024 $ 18 $ 5 2025 16 4 2026 13 4 2027 12 3 2028 10 3 2029 and thereafter 51 15 Total lease payments 120 34 Less: imputed interest 21 6 Total $ 99 $ 28

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note S. Commitments and Contingencies Other Long-Term Commitments Cabot has entered into long-term purchase agreements primarily for the purchase of raw materials. Under certain of these agreements, the quantity of material being purchased is fixed, but the price paid changes as market prices change. Raw materials purchased under these agreements were $ 370 million, $ 512 million and $ 405 million during fiscal 2023, 2022 and 2021, respectively. Included in those raw materials purchased are purchases from noncontrolling shareholders of consolidated subsidiaries of $ 192 million, $ 235 million and $ 135 million during fiscal 2023, 2022 and 2021, respectively. Accounts payable and accrued liabilities owed to noncontrolling shareholders as of September 30, 2023 and 2022, were $ 11 million and $ 31 million, respectively. For these purchase commitments, the amounts included in the table below are based on market prices as of September 30, 2023 which may differ from actual market prices at the time of purchase. Payments Due by Fiscal Year 2024 2025 2026 2027 2028 Thereafter Total (In millions) Reinforcement Materials $ 208 $ 185 $ 181 $ 161 $ 101 $ 1,266 $ 2,102 Performance Chemicals 41 38 36 36 21 211 $ 383 Total $ 249 $ 223 $ 217 $ 197 $ 122 $ 1,477 $ 2,485 The Company has also entered into long-term purchase agreements primarily for services related to information technology, which are not included in the table above, that total $ 19 million as of September 30, 2023, the majority of which is expected to be paid within the n ext 5 y ears. Guarantee Agreements Cabot has provided certain indemnities pursuant to which it may be required to make payments to an indemnified party in connection with certain transactions and agreements. In connection with certain acquisitions and divestitures, Cabot has provided routine indemnities with respect to such matters as environmental, tax, insurance, product and employee liabilities. In connection with various other agreements, including service and supply agreements with customers, Cabot has provided indemnities for certain contingencies and routine warranties. Cabot is unable to estimate the maximum potential liability for these types of indemnities as a maximum obligation is not explicitly stated in most cases and the amounts, if any, are dependent upon the outcome of future contingent events, the nature and likelihood of which cannot be reasonably estimated. The duration of the indemnities vary, and in many cases are indefinite. Cabot has not recorded any liability for these indemnities in the consolidated financial statements, except as otherwise disclosed. Self-Insurance and Retention for Certain Contingencies The Company is partially self-insured for certain third-party liabilities globally, as well as workers’ compensation and employee medical benefits in the United States. The third-party and workers’ compensation liabilities are managed through a wholly-owned insurance captive and the related liabilities are included in the consolidated financial statements. The employee medical obligations are managed by a third-party provider and the related liabilities are included in the consolidated financial statements. To limit Cabot’s potential liabilities for these risks, however, the Company purchases insurance from third parties that provides stop-loss protection. The self-insured liability in fiscal 2023 for third-party liabilities was $ 500,000 per accident for auto, $ 2 million per occurrence for all other, $ 1 million per accident for U.S. workers’ compensation, and the retention for medical costs in the United States is at most $ 275,000 per person per annum. Contingencies Cabot is a defendant, or potentially responsible party, in various lawsuits and environmental proceedings wherein substantial amounts are claimed or at issue. Environmental Matters As of September 30, 2023 and 2022, Cabot had $ 5 million and $ 4 million, respectively, reserved for environmental matters, which is included in Accounts payable and accrued liabilities and Other liabilities in the Consolidated Balance sheets. These environmental matters mainly relate to former operations. The Company’s reserves for environmental matters represent Cabot’s best estimates of the probable costs to be incurred at those sites where costs are reasonably estimable based on the Company’s analysis of the extent of clean up required, alternative clean-up methods available, abilities of other responsible parties to contribute and its interpretation of laws and regulations applicable to each site. Cabot reviews the adequacy of the reserves as circumstances change at individual sites and adjusts the reserves as appropriate. Almost all of Cabot’s environmental issues relate to sites that are mature and have been investigated and studied and, in many cases, are subject to agreed upon remediation plans. However, depending on the results of future testing, changes in risk assessment practices, remediation techniques and regulatory requirements, newly discovered conditions, and other factors, it is reasonably possible that the Company could incur additional costs in excess of environmental reserves currently recorded. Management estimates, based on the latest available information, that any such future environmental remediation costs that are reasonably possible to be in excess of amounts already recorded would be immaterial to the Company’s consolidated financial statements. Charges for environmental expense were $ 1 million in both fiscal 2023 and fiscal 2022, and less than $ 1 million in fiscal 2021 and are included in Cost of sal es in the Consolidated Statements of Operations. Cash payments related to these environmental matters were $ 1 million in fiscal 2023 and $ 2 million in both fiscal 2022 and fiscal 2021. The Company anticipates that expenditures related to these environmental matters will be made over a number of years. The operation and maintenance component of the reserve for environmental matters was $ 3 million at both September 30, 2023 and 2022. In November 2013, Cabot entered into a Consent Decree with the EPA and the Louisiana Department of Environmental Quality (“LDEQ”) regarding Cabot’s three carbon black manufacturing facilities in the U.S. This settlement is related to EPA’s national enforcement initiative focused on the U.S. carbon black manufacturing sector alleging non-compliance with certain regulatory and permitting requirements under The Clean Air Act, including the New Source Review (“NSR”) construction permitting requirements. Pursuant to this settlement, Cabot has installed technology controls for the reduction of sulfur dioxide and nitrogen oxide emissions at two of its plants and is in the process of installing these controls at the third plant. Cabot is currently in discussions with the EPA and LDEQ to extend its compliance date at the third plant to 2024 based upon force majeure events primarily related to the COVID-19 pandemic. 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. Generally, these respirator liabilities involve claims for personal injury, including asbestosis, silicosis and coal worker’s pneumoconiosis (“CWP”), allegedly resulting from the use of respirators that are alleged to have been negligently designed and/or labeled. At no time did this respiratory product line represent a significant portion of the respirator market. The subsidiary transferred the business to Aearo Technologies (“Aearo”) in July 1995. Cabot agreed to have the subsidiary retain certain liabilities associated with exposure to asbestos and silica while using respirators prior to the 1995 transaction so long as Aearo paid, and continues to pay, Cabot an annual fee of $400,000. Aearo can discontinue payment of the fee at any time, in which case it will assume the responsibility for and indemnify Cabot against those liabilities which Cabot’s subsidiary had agreed to retain. The Company anticipates that it will continue to receive payment of the $400,000 fee from Aearo and thereby retain these liabilities for the foreseeable future. Cabot has no liability in connection with any products manufactured by Aearo after 1995. Because of the difficulty in determining when a particular respirator was manufactured, Aearo and Cabot have applied the retention of liabilities under the 1995 agreement to claims arising out of the alleged use of respirators involving exposure to asbestos, silica or silica products prior to January 1, 1997. On July 26, 2022, Aearo voluntarily filed for Chapter 11 bankruptcy protection with the stated goal of establishing a trust, funded by Aearo and its parent 3M, to satisfy respirator and other unrelated claims related to earplug products determined to be entitled to compensation. On June 9, 2023, the court dismissed Aearo’s bankruptcy case based on motions filed by various creditors in the case. Aearo appealed the decision but did not seek to stay the dismissal, which made the dismissal effective immediately and ended the automatic bankruptcy stay. In August 2023, Aearo entered into a settlement agreement to resolve the unrelated earplug product claims. As a result of this settlement, Aearo’s appeals in the bankruptcy proceedings have been stayed. In addition to Cabot’s subsidiary and as described above, other parties are responsible for significant portions of the costs of respirator liabilities, leaving Cabot’s subsidiary with a portion of the liability in only some of the pending cases. These parties include Aearo, AO, AO’s insurers, another former owner and its insurers and a third-party manufacturer of respirators formerly sold under the AO brand and its insurers (collectively, with the Company’s subsidiary, the “Payor Group”). Cabot has contributed to the Payor Group’s defense and settlement costs with respect to a percentage of pending claims depending on several factors, including the period of alleged product use. In order to quantify Cabot’s estimated share of liability for pending and future respirator liability claims, Cabot has periodically engaged, through counsel, the assistance of Gnarus Advisors, LLC (“Gnarus”), a consulting firm in the field of tort liability valuation. The methodology used to estimate the liability addresses the complexities surrounding Cabot’s potential liability by making assumptions about Cabot’s likely exposure based on various factors, including the Payor Group’s historical experience with these claims, the number of future claims and the cost to resolve pending and future claims. Using those and other assumptions, the Company estimates the costs that would be incurred in defending and resolving both currently pending and future claims. As of September 30, 2023 and 2022, the Company had $ 38 million and $ 39 million, respectively, reserved for its estimated share of liability for pending and future respirator claims, the majority of which the Company expects to incur over the next ten years . The reserve is included in Other liabilities and Accounts payable and accrued liabilities on the Consolidated Balance Sheets. In fiscal 2023, 2022 and 2021, the Company recorded a charge of $ 8 million, $ 6 million and $ 25 million, respectively, related to the respirator liability which was included in Selling and administrative expense in the Consolidated Statements of Operations. The Company made payments related to its respirator liability of $ 9 million in fiscal 2023, $ 11 million in fiscal 2022 and $ 37 million in fiscal 2021. The majority of the payments in fiscal 2021 related to a February 2020 settlement agreement in which Cabot, with certain members of the Payor Group, resolved 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 current estimate of the cost of its share of pending and future respirator liability claims is based on facts and circumstances existing at this time, including the number and nature of the remaining claims. 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 or changes in our assessment of the viability of these claims, (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 payment of respirator claims , (ix) exhaustion or changes in the recoverability of the insurance coverage maintained by certain members of the Payor Group, or a change in the availability of the indemnity provided by a former owner of AO, (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. The Company cannot determine the impact of these potential developments on its current estimate of its share of liability for existing and future 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, it is reasonably possible that the liabilities for existing and future claims could change in the near term and that change could be material. Brazil Indirect Tax Settlements The Company previously filed claims with the Brazilian tax authorities challenging the calculation of certain indirect taxes related to local social contributions for the years 2012 through 2019. During the third quarter of fiscal 2021, the Brazilian Federal Supreme Court rendered a final unappealable decision that clarified the methodology companies should use in the calculation. As a result of this decision, the Company is entitled to recover credits and associated interest related to the historical periods for overpayment of these indirect taxes to be used to offset future Brazilian tax liabilities. As such, the Company recorded a $ 12 million benefit during fiscal 2021 of which $ 9 million, related to the credit recovery was included in Net sales and other operating revenues and $ 3 million, related to interest income was included in Other income (expense) in the Consolidated Statement of Operations. 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.

Financial Information by Segmen

Financial Information by Segment & Geographic Area	12 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Financial Information by Segment & Geographic Area	Note T. Financial Information by Segment & Geographic Area Segment Information 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 two reportable segments: Reinforcement Materials and Performance Chemicals. The Company’s former Purification Solutions business was a separate reportable segment prior to divestiture in the second quarter of fiscal 2022. Income (loss) from operations before income taxes (“Segment EBIT”) is presented for each reportable segment in the financial information by the reportable segment table below on the line entitled Income (loss) from operations before taxes. Segment EBIT excludes 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, royalties, Net income (loss) attributable to noncontrolling interests, net of tax, and discounting charges for certain Notes receivable, but excludes Interest expense, foreign currency transaction gains and losses, interest income, dividend income, unearned revenue, general unallocated expense and unallocated corporate costs. Segment assets exclude cash, short-term investments, cost investments, income taxes receivable, deferred taxes and headquarters’ assets, which are included in unallocated and other. Expenditures for additions to long-lived assets include total equity and other investments (including available-for-sale securities) and property, plant and equipment. Reinforcement Materials Carbon black is a form of elemental carbon that is manufactured in a highly controlled process to produce particles and aggregates of varied size, structure and surface chemistry, resulting in many different performance characteristics for a wide variety of applications. Reinforcing carbons (a class of carbon blacks manufactured by Cabot) are used to enhance the physical properties of the systems and applications in which they are incorporated. The Company’s reinforcing carbons products are used in tires and industrial products. Reinforcing carbons have traditionally been used in the tire industry as a rubber reinforcing agent to increase tread durability and are also used as a performance additive to reduce rolling resistance and improve traction. In industrial products such as hoses, belts, extruded profiles and molded goods, reinforcing carbons are used to improve the physical performance of the product, including the product’s physical strength, fluid resistance, conductivity and resistivity. In addition to its reinforcing carbons products, the Company manufactures engineered elastomer composites (“E2C®”) solutions that are composites of reinforcing carbons and rubber made using the Company’s patented elastomer composites manufacturing process. These composites improve abrasion/wear resistance, reduce fatigue of rubber parts and reduce rolling resistance compared to reinforcing carbons/rubber compounds made entirely by conventional rubber mix methods enabling rubber product manufacturers to reduce the need to make performance trade-offs. Performance Chemicals The Performance Chemicals segment aggregates the specialty carbons, specialty compounds, fumed metal oxides, battery materials, inkjet colorants and aerogel product lines. In Performance Chemicals, the Company designs, manufactures and sells materials that deliver performance in a broad range of customer applications across the automotive, construction, infrastructure, inkjet printing, electronics and consumer products sectors, and applications related to generation, transmission and storage of energy. The Company’s focus areas for growth include conductive additives and other materials for battery applications, and inkjet dispersions for post print corrugated packaging applications. The Company’s specialty carbons are used to impart color, provide rheology control, enhance conductivity and static charge control, provide UV protection, enhance mechanical properties and provide formulation flexibility through surface treatment. These specialty carbon products are used in a wide variety of applications, such as inks, coatings, cables, plastics, adhesives, toners, batteries and displays. Cabot’s masterbatch and conductive compound products, which Cabot refers to as “specialty compounds”, are formulations derived from specialty carbons mixed with polymers and other additives. These products are generally used by plastic resin producers and converters in applications for the automotive, industrial, packaging, infrastructure, agricultural, consumer products, and electronics industries. As an alternative to directly mixing specialty carbon blacks, these formulations offer greater ease of handling and help customers achieve their desired levels of dispersion and color and manage the addition of small doses of additives. In addition, Cabot’s electrically conductive compound products generally are used to help ensure uniform conductive performance and reduce risks associated with electrostatic discharge in plastics applications. The Company’s battery materials products include its conductive additives and fumed alumina, which are used principally in advanced lead acid and lithium-ion batteries used in electric vehicles. The Company’s conductive additives consist of conductive carbons, carbon nanotubes and carbon nano structures, and blends of these materials, each of which offers different levels of conductivity and formulation flexibility for battery manufacturers to address performance (energy density, fast charging), cost and safety. In lithium-ion batteries, the Company’s conductive additives are used in both cathode and anode applications to increase energy density by providing a conductive network between active materials. Fumed alumina is used to reduce cathode material and electrolyte decomposition and improve capacity retention leading to longer cycle life. Fumed silica is an ultra-fine, high-purity particle used as a reinforcing, thickening, abrasive, thixotropic, suspending or anti-caking agent in a wide variety of products for the automotive, construction, microelectronics, batteries, and consumer products industries. These products include adhesives, sealants, cosmetics, batteries, inks, toners, silicone elastomers, coatings, polishing slurries and pharmaceuticals. In addition to its battery application, fumed alumina, also an ultra-fine, high-purity particle, is used as an abrasive, absorbent or barrier agent in a variety of products, such as inkjet media, lighting, coatings, cosmetics and polishing slurries. Aerogel is a hydrophobic, silica-based particle with a high surface area that is used in a variety of thermal insulation and specialty chemical applications. In the building and construction industry, the product is used in insulative sprayable plasters and composite building products, as well as translucent skylight, window, wall and roof systems for insulating eco-daylighting applications. In the specialty chemicals industry, the product is used to provide matte finishing, insulating and thickening properties for use in a variety of applications, including thermal management for lithium-ion batteries. The Company’s inkjet colorants are high-quality pigment-based black and color dispersions and inks. The Company’s dispersions are based on patented pigment surface modification technology and polymer encapsulation technology. The dispersions are used in aqueous inkjet inks to impart color, sharp print characteristics and durability, while maintaining high printhead reliability. These products are used in various inkjet printing applications, including traditional work-from-home and corporate office settings, and, increasingly, in commercial and corrugated packaging printing, that all require a high level of dispersibility and colloidal stability. Our inkjet inks, which utilize our pigment-based colorant dispersions, are used in the commercial printing segment for graphic arts. Purification Solutions Cabot divested its Purification Solutions business on March 1, 2022. Refer to Note D for the terms of this transaction. Financial information by reportable segment is as follows: Years Ended September 30 Reinforcement Performance Purification (1) Segment Unallocated (2) Consolidated (In millions) 2023 Revenues from external customers (4) $ 2,563 $ 1,225 $ — $ 3,788 $ 143 $ 3,931 Depreciation and amortization $ 70 $ 72 $ — $ 142 $ 2 $ 144 Equity in earnings of affiliated companies $ 2 $ 3 $ — $ 5 $ — $ 5 Income (loss) from operations (5) $ 482 $ 125 $ — $ 607 $ ( 156 ) $ 451 Assets (6) $ 1,632 $ 1,473 $ — $ 3,105 $ 499 $ 3,604 Total expenditures for additions to long-lived (7) $ 149 $ 108 $ — $ 257 $ 8 $ 265 2022 Revenues from external customers (3)(4) $ 2,673 $ 1,388 $ 97 $ 4,158 $ 163 $ 4,321 Depreciation and amortization $ 70 $ 72 $ 3 $ 145 $ 1 $ 146 Equity in earnings of affiliated companies $ 4 $ 5 $ 1 $ 10 $ — $ 10 Income (loss) from operations (5) $ 408 $ 234 $ — $ 642 $ ( 307 ) $ 335 Assets (6) $ 1,691 $ 1,458 $ — $ 3,149 $ 376 $ 3,525 Total expenditures for additions to long-lived (7) $ 114 $ 100 $ 3 $ 217 $ 4 $ 221 2021 Revenues from external customers (3)(4) $ 1,838 $ 1,156 $ 257 $ 3,251 $ 158 $ 3,409 Depreciation and amortization $ 70 $ 73 $ 16 $ 159 $ 1 $ 160 Equity in earnings of affiliated companies $ — $ 2 $ 2 $ 4 $ ( 1 ) $ 3 Income (loss) from operations (5) $ 329 $ 211 $ 10 $ 550 $ ( 144 ) $ 406 Assets (6) $ 1,421 $ 1,325 $ 283 $ 3,029 $ 277 $ 3,306 Total expenditures for additions to long-lived (7) $ 104 $ 80 $ 9 $ 193 $ 5 $ 198 (1) Cabot divested its Purification Solutions business on March 1, 2022. Refer to Note D for the terms of this transaction. (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) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation. The allocation of such revenue resulted in an increase of $ 98 million and $ 57 million in the Reinforcement Materials segment and $ 16 million and $ 8 million in the Performance Chemicals segment, with an offsetting decrease in Unallocated and Other revenue for fiscal 2022 and fiscal 2021, respectively. There was no impact to Consolidated Total Revenue from external customers. (4) 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 are summarized as follows: Years Ended September 30 2023 2022 2021 (In millions) Shipping and handling fees $ 132 $ 162 $ 153 By-product sales 5 8 8 Other 6 ( 7 ) ( 3 ) Total $ 143 $ 163 $ 158 (5) Consolidated Total Income (loss) from operations before income taxes reconciles to Income (loss) from operations before income taxes and equity in earnings of affiliated companies on the Consolidated Statements of Operations. Total Income (loss) from operations before income taxes that are categorized as Unallocated and Other includes: Years Ended September 30 2023 2022 2021 (In millions) Interest expense $ ( 90 ) $ ( 56 ) $ ( 49 ) Certain items: (a) Gain on sale of land 1 17 — Legal and environmental matters and reserves (Note S) ( 10 ) ( 9 ) ( 25 ) Argentina controlled currency devaluation loss ( 7 ) — — Acquisition and integration-related charges ( 4 ) ( 6 ) ( 5 ) Global restructuring activities ( 4 ) ( 3 ) ( 11 ) Loss on sale of business and asset impairment charge ( 3 ) ( 207 ) — Other certain items ( 2 ) — ( 1 ) Gain on bargain purchase of a business (Note C) — 24 — Specialty Fluids divestiture related benefit — 5 — Employee benefit plan settlement and other charges — 1 ( 4 ) Purification Solutions divestiture related charges — ( 5 ) — Indirect tax settlement credits — — 12 Total certain items, pre-tax ( 29 ) ( 183 ) ( 34 ) Unallocated corporate costs (b) ( 54 ) ( 59 ) ( 58 ) General unallocated income (expense) (c) 22 1 — Less: Equity in earnings of affiliated companies, net of tax (d) 5 10 3 Total $ ( 156 ) $ ( 307 ) $ ( 144 ) (a) Certain items are items that management does not consider representative of operating segment results and they are, therefore, excluded from Segment EBIT. (b) Unallocated corporate costs 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, and unrealized holding gains (losses) for investments. (d) Equity in earnings of affiliated companies, net of tax is included in Segment EBIT and is removed from Unallocated and other to reconcile to income (loss) from operations before taxes and equity in earnings from affiliated companies. (6) Unallocated and Other assets include cash, marketable securities, cost investments, income taxes receivable, deferred taxes, headquarters’ assets and current and non-current assets held for sale. (7) Expenditures for additions to long-lived assets include total equity and other investments (including available-for-sale securities) and property, plant and equipment. Geographic Information Revenues from external customers attributable to an individual country, other than the U.S. and China, were not material for disclosure. Revenues from external customers by individual country are summarized as follows: Years Ended September 30 2023 2022 2021 (In millions) United States $ 738 $ 842 $ 668 China 972 1,129 858 Other countries 2,221 2,350 1,883 Total $ 3,931 $ 4,321 $ 3,409 Each of the Company’s segments operates globally. In addition to presenting Revenue from external customers by reportable segment, the following tables further disaggregate Revenue from external customers by geographic region. Year Ended September 30, 2023 Reinforcement Performance Purification Consolidated Total (In millions) Americas $ 1,046 $ 379 $ — $ 1,425 Asia Pacific 995 491 — 1,486 Europe, Middle East and Africa 522 355 — 877 Segment revenues from external customers 2,563 1,225 — 3,788 Unallocated and other 143 Net sales and other operating revenues $ 3,931 Year Ended September 30, 2022 Reinforcement (1) Performance (1) Purification Consolidated Total (In millions) Americas $ 1,072 $ 419 $ 43 $ 1,534 Asia Pacific 1,049 567 14 1,630 Europe, Middle East and Africa 552 402 40 994 Segment revenues from external customers 2,673 1,388 97 4,158 Unallocated and other 163 Net sales and other operating revenues $ 4,321 (1) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation. Year Ended September 30, 2021 Reinforcement (1) Performance (1) Purification Consolidated Total (In millions) Americas $ 708 $ 311 $ 110 $ 1,129 Asia Pacific 777 489 34 $ 1,300 Europe, Middle East and Africa 353 356 113 822 Segment revenues from external customers 1,838 1,156 257 3,251 Unallocated and other 158 Net sales and other operating revenues $ 3,409 (1) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation. Property, plant and equipment attributable to an individual country, other than the U.S. and China, were not material for disclosure. Property, plant and equipment information by individual country is summarized as follows: Years Ended September 30 2023 2022 (In millions) United States $ 588 $ 524 China 356 333 Other countries 468 413 Total $ 1,412 $ 1,270

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Cabot and its wholly-owned subsidiaries and majority-owned and controlled subsidiaries. Additionally, Cabot considers consolidation of entities over which control is achieved through means other than voting rights, of which there were none in the periods presented. Intercompany transactions have been eliminated in consolidation.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents include all highly liquid investments with a maturity of three months or less at date of acquisition. Cabot continually assesses the liquidity of cash equivalents and, as of September 30, 2023, has determined that they are readily convertible to cash.
Inventories	Inventories Inventories are stated at the lower of cost or net realizable value. The cost of inventories is determined using the first-in, first-out 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.
Investments	Investments The Company has investments in equity affiliates and marketable securities. As circumstances warrant, all investments are subject to periodic impairment reviews. Unless consolidation is required, investments in equity affiliates, where Cabot generally owns between 20 % and 50 % of the affiliate, are accounted for using the equity method. Cabot records its share of the equity affiliate’s results of operations based on its percentage of ownership of the affiliate. Dividends declared from equity affiliates are a return on investment and are recorded as a reduction to the equity investment value. At both September 30, 2023 and 2022, Cabot had equity affiliate investments of $ 20 million. Dividends declared and received from these investments were $ 2 million, $ 1 million and $ 5 million in fiscal 2023, 2022 and 2021, respectively.
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 an acquisition are allocated to the assets acquired and liabilities assumed 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 and is subject to impairment testing annually, 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, specialty carbons and battery materials product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of September 30, 2023. 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. 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 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. The fair value is also benchmarked against the value calculated from a market approach using the guideline public company method. In fiscal 2023, the Company’s qualitative assessment, performed as of August 31, 2023, indicated that the fair values of the Reinforcement Materials, fumed metal oxides, specialty compounds, specialty carbons and battery materials reporting units were in excess of their carrying values.
Long-Lived Assets Impairment	Long-lived Assets Impairment Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable. 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. 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 market value, a discounted cash flow model may be used to determine the fair value of the asset.
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 generally 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. Cabot capitalizes interest costs when they are part of the cost of acquiring and constructing certain assets that require a period of time to prepare for their intended use. During fiscal 2023, 2022 and 2021, Cabot capitalized $ 6 million, $ 3 million and $ 1 million of interest costs, respectively. These amounts are amortized over the lives of the related assets when they are placed in service.
Asset Retirement Obligations	Asset Retirement Obligations Cabot estimates incremental costs for special handling, removal and disposal of materials that may or will give rise to conditional asset retirement obligations (“ARO”) and then discounts the expected costs back to the current year using a credit adjusted risk-free rate. Cabot recognizes ARO liabilities and costs when they are probable and can be reasonably estimated. In certain instances, Cabot has not recorded a reserve for AROs because the timing of disposal of the underlying asset is unknown. The ARO reserves were $ 11 million and $ 10 million at September 30, 2023 and 2022, respectively. The ARO balances are included in Accounts payable and accrued liabilities and Other liabilities on the Consolidated Balance Sheets.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the majority of Cabot’s foreign subsidiaries is the local currency in which the subsidiary operates. Assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet dates. Income and expense items are translated at average monthly exchange rates during the year. The functional currency of Cabot’s foreign subsidiaries that operate in a highly inflationary economy is the U.S. dollar. Cabot’s operations in highly inflationary economies are not material. Unrealized currency translation adjustments (“CTA”) are included as a separate component of Accumulated other comprehensive income (loss) (“AOCI”) within stockholders’ equity. Realized and unrealized foreign currency gains and losses arising from transactions denominated in currencies other than the subsidiary’s functional currency are reflected in earnings with the exception of (i) intercompany transactions considered to be of a long-term investment nature; (ii) income taxes upon future repatriation of unremitted earnings from non-U.S. subsidiaries that are not indefinitely reinvested; and (iii) foreign currency borrowings designated as net investment hedges. Gains or losses arising from these transactions are included within the CTA component of Other comprehensive income (loss). In fiscal 2023, 2022 and 2021, net foreign currency transaction loss of $ 35 million, $ 13 million, and $ 6 million, respectively, is included in Other income (expense) in the Consolidated Statements of Operations.
Share Repurchases	Share Repurchases Periodically, Cabot repurchases shares of the Company’s common stock in the open market or in privately negotiated transactions under the authorization approved by the Board of Directors. The Company retires the repurchased shares and records the excess of the purchase price over par value to additional paid-in capital (“APIC”) until such amount is reduced to zero and then charges the remainder against retained earnings.
Financial Instruments	Financial Instruments Cabot’s financial instruments consist primarily of cash and cash equivalents, accounts and notes receivable, investments, accounts payable and accrued liabilities, short-term and long-term debt, and derivative instruments. The carrying values of Cabot’s financial instruments approximate fair value with the exception of fixed rate long-term debt, which is recorded at amortized cost. The fair values of the Company’s financial instruments are based on quoted market prices, if such prices are available. In situations where quoted market prices are not available, the Company relies on valuation models to derive fair value. Such valuations take into account the ability of the financial counterparty to perform and the Company’s own credit risk. Cabot uses derivative financial instruments primarily for purposes of hedging the exposures to fluctuations in foreign currency exchange rates, which exist as part of its on-going business operations. Cabot does not enter into derivative contracts for speculative purposes, nor does it hold or issue any derivative contracts for trading purposes. All derivatives are recognized on the Consolidated Balance Sheets at fair value. Where Cabot has a legal right to offset derivative settlements under a master netting agreement with a counterparty, derivatives with that counterparty are presented on a net basis. The changes in the fair value of derivatives are recorded in either earnings or AOCI, depending on whether or not the instrument is designated as part of a hedge transaction and, if designated as part of a hedge transaction, the type of hedge transaction. The gains or losses on derivative instruments reported in AOCI are reclassified to earnings in the period in which earnings are affected by the underlying hedged item. The ineffective portion of all hedges is recognized in earnings during the period in which the ineffectiveness occurs. In accordance with Cabot’s risk management strategy, the Company may enter into certain derivative instruments that may not be designated as hedges for hedge accounting purposes. Although these derivatives are not designated as hedges, the Company believes that such instruments are closely correlated with the underlying exposure, thus managing the associated risk. The Company records in earnings the gains or losses from changes in the fair value of derivative instruments that are not designated as hedges. Cash movements associated with these instruments are presented in the Consolidated Statements of Cash Flows as Cash Flows from Operating Activities because the derivatives are designed to mitigate risk to the Company’s cash flow from operations.
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 which 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. Substantially all revenue from product sales is based on a point in time model and is recognized 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. For contracts where we complete our performance obligation prior to our right to consideration or contracts where we receive consideration prior to completing our performance obligation we record a contract asset or a contract liability, respectively, on the Consolidated Balance Sheets. Shipping and handling activities that occur after the transfer of control to the customer are billed to customers and are recorded as sales revenue, as the Company considers these to be fulfillment costs. These 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. Payment terms typically range from zero to ninety days . 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.
Cost of Sales	Cost of Sales Cost of sales consists of the cost of raw and packaging materials, direct manufacturing costs, depreciation, internal transfer costs, inspection costs, inbound and outbound freight and shipping and handling costs, plant purchasing and receiving costs and other overhead expenses necessary to manufacture the products.
Accounts and Notes Receivable	Accounts and Notes Receivable Trade receivables are recorded at the invoiced amount and generally do not bear interest. Cabot maintains allowances for doubtful accounts based on an assessment of the collectability of specific customer accounts, the aging of accounts receivable and other economic information on both a historical and prospective basis. Customer account balances are charged against the allowance when it is probable the receivable will not be recovered. There were no material changes in the allowance for any of the years presented.
Stock-Based Compensation	Stock-based Compensation Cabot recognizes compensation expense for stock-based awards granted to employees using the fair value method. Under the fair value recognition provisions, stock-based compensation cost is measured at the grant date based on the fair value of the award, and is recognized as expense over the service period, which generally represents the vesting period, and includes an estimate of what level of performance the Company will achieve for Cabot’s performance-based stock awards. Cabot calculates the fair value of its stock options using the Black-Scholes option pricing model. The fair value of restricted stock units is determined using the closing price of Cabot stock on the day of the grant. The Company recognizes forfeitures as they occur.
Selling and Administrative Expenses	Selling and Administrative Expenses Selling and administrative expenses consist of salaries and fringe benefits of sales and office personnel, general office expenses and other expenses not directly related to manufacturing operations.
Research and Technical Expenses	Research and Technical Expenses Research and technical expenses include salaries, equipment and material expenditures, and contractor fees and are expensed as incurred.
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. Service cost is included with other employee compensation costs within Cost of sales, Selling and administrative expenses, or Research and technical expenses. The Company recognizes actuarial gains and losses and prior service costs and credits as a component of Other comprehensive income (loss), net of tax, which are subsequently amortized into earnings as a component 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 and pension and post-retirement related adjustments.
Income Taxes	Income Taxes Deferred income taxes are determined based on the estimated future tax effects of differences between financial statement carrying amounts and the tax bases of existing assets and liabilities. Deferred tax assets are recognized to the extent that realization of those assets is considered to be more likely than not. A valuation allowance is established for deferred taxes when it is more likely than not that all or a portion of the deferred tax assets will not be realized. Provisions are made for the U.S. income tax liability and additional non-U.S. taxes on the undistributed earnings of non-U.S. subsidiaries, except for amounts Cabot has designated to be indefinitely reinvested. Cabot records benefits for uncertain tax positions based on an assessment of whether the position is more likely than not to be sustained by the taxing authorities. If this threshold is not met, no tax benefit of the uncertain tax position is recognized. If the threshold is met, the tax benefit that is recognized is the largest amount that is greater than 50 % likely of being realized upon ultimate settlement. This analysis presumes the taxing authorities’ full knowledge of the positions taken and all relevant facts, but does not consider the time value of money. The Company also accrues for interest and penalties on its uncertain tax positions and includes such charges in its income tax provision in the Consolidated Statements of Operations.
Contingencies	Contingencies Cabot accrues costs related to contingencies when it is probable that a liability has been incurred and the amount can be reasonably estimated. Contingencies could arise from litigation, environmental remediation or contractual arrangements. When a single liability amount cannot be reasonably estimated, but a range can be reasonably estimated, Cabot accrues the amount that reflects the best estimate within that range or the low end of the range if no estimate within the range would be considered more likely than any other estimate. The amount accrued is determined through the evaluation of various information, which could include claims, settlement offers, demands by government agencies, estimates performed by independent third parties, identification of other responsible parties and an assessment of their ability to contribute, and our prior experience. Cabot does not reduce its estimated liability for possible recoveries from insurance carriers. Proceeds from insurance carriers are recorded when realized by either the receipt of cash or a contractual agreement.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make certain estimates and assumptions that affect the reported amount of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reported period. Actual results could differ from those estimates.

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Sep. 30, 2023
Inventory Disclosure [Abstract]
Components of Company's Inventories	Inventories, net of obsolete, unmarketable and slow-moving reserves, are as follows: September 30 2023 2022 (In millions) Raw materials $ 148 $ 182 Finished goods 374 427 Other (1) 63 55 Total $ 585 $ 664 (1) Other inventory is comprised of certain spare parts and supplies.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Sep. 30, 2023
Property Plant And Equipment [Abstract]
Components of Property, Plant and Equipment	Property, plant and equipment consists of the following: September 30 2023 2022 (In millions) Land and land improvements $ 72 $ 75 Buildings 576 553 Machinery and equipment 2,622 2,473 Other 228 229 Construction in progress 329 224 Total property, plant and equipment 3,827 3,554 Less: Accumulated depreciation ( 2,415 ) ( 2,284 ) Net property, plant and equipment $ 1,412 $ 1,270

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Sep. 30, 2023
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 fiscal year ended September 30, 2023 are as follows Reinforcement Performance Total (In millions) Balance at September 30, 2022 $ 46 $ 83 $ 129 Foreign currency impact 5 — 5 Balance at September 30, 2023 $ 51 $ 83 $ 134
Schedule of Intangible Assets with Finite Lives	The following table provides information regarding the Company’s intangible assets with finite lives: September 30, 2023 September 30, 2022 Gross Accumulated Net Gross Accumulated Net (In millions) Developed technologies $ 34 $ ( 10 ) $ 24 $ 34 $ ( 8 ) $ 26 Trademarks 2 ( 1 ) 1 2 ( 1 ) 1 Customer relationships 65 ( 30 ) 35 59 ( 23 ) 36 Total intangible assets $ 101 $ ( 41 ) $ 60 $ 95 $ ( 32 ) $ 63

Accounts Payable, Accrued Lia_2

Accounts Payable, Accrued Liabilities and Other Liabilities (Tables)	12 Months Ended
	Sep. 30, 2023
Payables and Accruals [Abstract]
Components of Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities included in current liabilities consist of the following: September 30 2023 2022 (In millions) Accounts payable $ 438 $ 533 Accrued employee compensation 55 66 Other accrued liabilities 107 108 Total $ 600 $ 707
Components of Other Long-Term Liabilities	Other long-term liabilities consist of the following: September 30 2023 2022 (In millions) Employee benefit plan liabilities $ 48 $ 51 Operating lease liabilities 84 83 Other accrued liabilities 99 100 Total $ 231 $ 234

Debt and Other Obligations (Tab

Debt and Other Obligations (Tables)	12 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Schedule of Long-Term Obligations	The Company’s long-term obligations, the fiscal year in which they mature and their respective interest rates are summarized below: September 30 2023 2022 (In millions) Variable Rate Debt: Revolving Credit Facility, expires fiscal 2027 $ — $ — Revolving Credit Facility - Euro, expires fiscal 2027 120 114 Total variable rate debt 120 114 Fixed Rate Debt: 3.4 % Notes due fiscal 2026 250 250 4.0 % Notes due fiscal 2029 300 300 5.0 % Notes due fiscal 2032 400 400 Medium-Term Notes due fiscal 2028 , 6.57 % — 7.28 % 8 8 Chinese Renminbi Debt, due fiscal 2024 , 4.3 % 4 4 Total fixed rate debt 962 962 Finance lease obligations (Note R) 28 29 Unamortized debt issuance costs and debt discount ( 8 ) ( 9 ) Total debt 1,102 1,096 Less current portion of long-term debt ( 8 ) ( 7 ) Total long-term debt $ 1,094 $ 1,089
Schedule of Future Years Payment	The aggregate principal amounts of long-term debt, excluding finance lease liabilities presented separately in Note R, due in each of the five years from fiscal 2024 through 2028 and thereafter are as follows: Years Ending September 30 Principal Payments (In millions) 2024 $ 4 2025 — 2026 250 2027 120 2028 8 Thereafter 700 Total $ 1,082

Derivatives (Tables)

Derivatives (Tables)	12 Months Ended
	Sep. 30, 2023
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 September 30, 2023 and 2022 to manage foreign currency risk. Notional Amount Description Borrowing September 30, 2023 September 30, 2022 Hedge 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 82 million USD 42 million No designation (1) At September 30, 2023, the Company’s forward foreign exchange contracts were denominated in Indonesian rupiah, Czech koruna, and Colombian peso. At September 30, 2022, the Company’s forward foreign exchange contracts were denominated in 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: Years Ended September 30 2023 2022 2021 2023 2022 2021 2023 2022 2021 Description Gain/(Loss) Recognized in AOCI (Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated (Gain)/Loss Recognized in Interest (In millions) Cross-currency swaps $ ( 13 ) $ 30 $ 7 $ ( 6 ) $ ( 6 ) $ ( 5 ) $ 2 $ 2 $ 2

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Sep. 30, 2023
Retirement Benefits [Abstract]
Change in Benefit Obligations and Change in Plan Assets	The following provides information about projected benefit obligations, plan assets, the funded status and weighted-average assumptions of the defined benefit pension and postretirement benefit plans: Years Ended September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Change in Benefit Obligations: Benefit obligation at beginning of $ 2 $ 133 $ 3 $ 221 $ 16 $ 13 $ 25 $ 19 Service cost — 3 — 4 — — — — Interest cost — 7 — 4 1 1 — 1 Plan participants’ contribution — 1 — 1 — — — — Foreign currency exchange rate — 6 — ( 27 ) — 1 — ( 2 ) (Gain) loss from changes in actuarial — ( 4 ) ( 1 ) ( 43 ) ( 1 ) ( 3 ) ( 4 ) ( 5 ) Benefits paid — ( 5 ) — ( 9 ) ( 2 ) ( 1 ) ( 3 ) — Settlem ents or curtailments — ( 2 ) — ( 2 ) — — ( 2 ) — Divestiture of a business — — — ( 16 ) — — — — Benefit obligation at end of year $ 2 $ 139 $ 2 $ 133 $ 14 $ 11 $ 16 $ 13 Years Ended September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Change in Plan Assets: Fair value of plan assets at beginning $ — $ 135 $ — $ 217 $ — $ — $ — $ — Actual return on plan assets — 4 — ( 35 ) — — — — Employer contribution — 4 — 5 2 1 5 — Plan participants’ contribution — 1 — 1 — — — — Foreign currency exchange rate — 7 — ( 24 ) — — — — Benefits paid — ( 5 ) — ( 9 ) ( 2 ) ( 1 ) ( 3 ) — Settlements or curtailments — ( 2 ) — ( 2 ) — — ( 2 ) — Expenses paid from assets — — — — — — — — Divestiture of a business — — — ( 18 ) — — — — Fair value of plan assets at end $ — $ 144 $ — $ 135 $ — $ — $ — $ — Funded status $ ( 2 ) $ 5 $ ( 2 ) $ 2 $ ( 14 ) $ ( 11 ) $ ( 16 ) $ ( 13 ) Recognized asset (liability) $ ( 2 ) $ 5 $ ( 2 ) $ 2 $ ( 14 ) $ ( 11 ) $ ( 16 ) $ ( 13 )
Assumptions Used to Determine Pension Benefit Obligations and Periodic Benefit Costs, Postretirement Benefit Obligations and Net Costs	Pension Assumptions and Strategy The following assumptions were used to determine the pension benefit obligations and periodic benefit costs as of and for the years ended September 30: 2023 2022 2021 Pension Benefits U.S. Foreign U.S. Foreign U.S. Foreign Actuarial assumptions as of the year-end Discount rate 6.0 % 4.7 % 5.5 % 4.5 % 2.2 % 2.1 % Rate of increase in compensation N/A 3.0 % 3.0 % 3.0 % N/A 2.9 % Cash balance interest credit rate 2.0 % 2.1 % 2.0 % 2.0 % 2.0 % 1.7 % Actuarial assumptions used to determine net Discount rate - benefit obligation 5.6 % 4.5 % 2.2 % 2.1 % 2.5 % 1.7 % Discount rate - service cost N/A 3.6 % N/A 2.0 % N/A 1.7 % Discount rate - interest cost 5.3 % 4.5 % 1.6 % 1.7 % 1.4 % 1.4 % Expected long-term rate of return on N/A 5.1 % N/A 3.5 % N/A 4.6 % Rate of increase in compensation N/A 3.0 % N/A 2.9 % N/A 3.0 % Cash balance interest credit rate 2.0 % 2.0 % 2.0 % 1.7 % 2.1 % 1.7 % Postretirement Assumptions and Strategy The following assumptions were used to determine the postretirement benefit obligations and net costs as of and for the years ended September 30: 2023 2022 2021 Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign Actuarial assumptions as of the year-end Discount rate 6.0 % 5.7 % 5.6 % 5.1 % 2.4 % 2.8 % Initial health care cost trend rate (1) 5.0 % 6.4 % — % 6.8 % 5.5 % 6.9 % Actuarial assumptions used to determine Discount rate - benefit obligation 5.6 % 5.1 % 2.4 % 2.8 % 2.1 % 2.4 % Discount rate - service cost 5.4 % 5.1 % 1.7 % 3.5 % 1.5 % 3.0 % Discount rate - interest cost 5.3 % 5.1 % 1.6 % 2.5 % 1.4 % 2.1 % Initial health care cost trend rate (1) — % 6.8 % 5.5 % 6.9 % 6.0 % 6.9 % (1) The initial health care cost trend rate is set at 5 % for the 2023 U.S. plan assumptions as the 2024 Medicare Part B premiums are expected to increase. The trend rates for all future years beyond 2024 also reflect expected 5 % increases. The initial health care cost trend rate was set at zero for the 2022 U.S. plan assumptions in light of the expected downward adjustment the U.S. government was expected to make to the 2023 Medicare Part B premiums, however, all trend rates beyond the initial year were set to 5 % .
Amounts Recognized in Consolidated Balance Sheets	Amounts recognized in the Consolidated Balance Sheets at September 30, 2023 and 2022 related to the Company's defined benefit pension and postretirement benefit plans were as follows: September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Other assets $ — $ 30 $ — $ 26 $ — $ — $ — $ — Accounts payable and accrued liabilities $ — $ ( 1 ) $ — $ ( 1 ) $ ( 2 ) $ ( 1 ) $ ( 2 ) $ ( 1 ) Other liabilities $ ( 2 ) $ ( 24 ) $ ( 2 ) $ ( 23 ) $ ( 12 ) $ ( 10 ) $ ( 14 ) $ ( 12 )
Amounts Recognized in AOCI	Amounts recognized in AOCI at September 30, 2023 and 2022 related to the Company's defined benefit pension and postretirement benefit plans were as follows: September 30 2023 2022 2023 2022 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Net actuarial (gain) loss $ — $ 24 $ — $ 23 $ ( 6 ) $ ( 7 ) $ ( 6 ) $ ( 4 ) Net prior service credit — ( 1 ) — ( 1 ) — — — — Balance in accumulated other $ — $ 23 $ — $ 22 $ ( 6 ) $ ( 7 ) $ ( 6 ) $ ( 4 )
Estimated Future Benefit Payments	Estimated Future Benefit Payments The Company expects that the following benefit payments will be made to plan participants in the years from 2024 to 2033: Pension Benefits Postretirement Benefits Years Ending September 30 U.S. Foreign U.S. Foreign (In millions) 2024 $ — $ 9 $ 2 $ 1 2025 $ — $ 9 $ 2 $ 1 2026 $ — $ 9 $ 2 $ 1 2027 $ — $ 11 $ 2 $ 1 2028 $ — $ 11 $ 2 $ 1 2029 - 2033 $ 1 $ 49 $ 6 $ 4
Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs	Net periodic defined benefit pension and other postretirement benefit costs include the following components: Years Ended September 30 2023 2022 2021 2023 2022 2021 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Service cost $ — $ 3 $ — $ 4 $ — $ 6 $ — $ — $ — $ — $ — $ — Interest cost — 7 — 4 — 3 1 1 — 1 — 1 E xpected return on plan — ( 7 ) — ( 6 ) — ( 10 ) — — — — — — A mortizatio n of n et l osses — ( 1 ) — 1 — 3 ( 1 ) — — — — — Settlements or — — — — 4 1 — — ( 1 ) — — — Other — — — — — 2 — — — — — — Net periodic (benefit) cost $ — $ 2 $ — $ 3 $ 4 $ 5 $ — $ 1 $ ( 1 ) $ 1 $ — $ 1
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss), Pre-Tax	Other changes in plan assets and benefit obligations recognized in Other comprehensive income (loss) are as follows: Years Ended September 30 2023 2022 2021 2023 2022 2021 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Net (gains) losses $ — $ 1 $ — $ ( 2 ) $ ( 2 ) $ ( 15 ) $ ( 1 ) $ ( 3 ) $ ( 4 ) $ ( 4 ) $ — $ ( 2 ) Prior service (credit) cost — — — — — ( 1 ) — — — — — Amortization of prior — 1 — ( 1 ) — ( 3 ) 1 — — — — — Loss on divestiture — — — ( 2 ) — — — — — — — — (Loss) g ain on settl ements — — — — ( 4 ) ( 1 ) — — 1 — — — Net changes recognized in (1) $ — $ 2 $ — $ ( 5 ) $ ( 6 ) $ ( 20 ) $ — $ ( 3 ) $ ( 3 ) $ ( 4 ) $ — $ ( 2 ) (1) The tax impact on pension and other postretirement benefit liability adjustments arising during the period was a tax provision of less than $ 1 million, a tax benefit of $ 3 million and a tax benefit of $ 8 million for fiscal 2023, 2022 and 2021, respectively.
Defined Benefit Pension Plans Weighted-Average Asset Allocations	The Company’s foreign defined benefit pension plans weighted-average asset allocations at September 30, 2023 and 2022 by asset category, are as follows: September 30 2023 2022 Equity securities 19 % 20 % Debt securities 31 % 68 % Real estate 10 % 7 % Cash and other securities (1) 40 % 5 % Total 100 % 100 % (1) The asset allocation is temporarily changed as a result of the insurance contracts Cabot Carbon Limited Pension Plan and Carbon Plastics Pension Plan purchased with plan assets in anticipation of the settlement discussed above.
Fair Value of Pension Plan Assets by Asset Category	The fair value of the Company’s pension plan assets at September 30, 2023 and 2022 by asset category is as follows: September 30 2023 2022 Quoted Prices in Significant Total Quoted Prices in Significant Total (In millions) Cash $ — $ — $ — $ 1 $ — $ 1 Direct investments: U.S government bonds — — — — — — U.S. corporate bonds — — — — — — Non-U.S. equities 6 — 6 4 — 4 Non-U.S. government bonds 2 — 2 1 — 1 Non-U.S. corporate bonds 3 — 3 2 — 2 Mortgage-backed securities — 1 1 — 1 1 Other fixed income 1 — 1 1 — 1 Total direct investments 12 1 13 8 1 9 Investment funds: Equity funds (1) — 21 21 — 23 23 Fixed income funds (2) — 38 38 — 86 86 Real estate funds (3) — 15 15 — 9 9 Cash equivalent funds 4 — 4 1 — 1 Other investment funds — — — — 1 1 Total investment funds 4 74 78 1 119 120 Alternative investments: Insurance contracts (4) — 52 52 — 5 5 Other alternative investments — 1 1 — — — Total alternative investments — 53 53 — 5 5 Total pension plan assets $ 16 $ 128 $ 144 $ 10 $ 125 $ 135 (1) The equity funds asset class includes funds that invest in U.S. equities as well as equity securities issued by companies incorporated, listed or domiciled in countries in developed and/or emerging markets. These companies may be in the small-, mid- or large-cap categories. (2) The fixed income funds asset class includes investments in high quality funds. High quality fixed income funds primarily invest in low-risk U.S. and non-U.S. government securities, investment-grade corporate bonds, mortgages and asset-backed securities. A significant portion of the fixed income funds include investment in long-term bond funds. (3) The real estate funds asset class includes funds that primarily invest in entities which are principally engaged in the ownership, acquisition, development, financing, sale and/or management of income-producing real estate properties, both commercial and residential. These funds typically seek long-term growth of capital and current income that is above average relative to public equity funds. (4) Insurance contracts held by the Company’s non-U.S. plans are issued by well-known, highly rated insurance companies.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation Expenses	The following table presents stock-based compensation expenses included in the Company’s Consolidated Statements of Operations: Years Ended September 30 2023 2022 2021 (In millions) Cost of sales $ 2 $ 3 $ 2 Selling and administrative expenses 16 18 17 Research and technical expenses 2 2 2 Stock-based compensation expense 20 23 21 Income tax benefit ( 2 ) ( 1 ) ( 1 ) Net stock-based compensation expense $ 18 $ 22 $ 20
Equity Incentive Plan Activity	The following table summarizes the total stock option and restricted stock unit activity in the equity incentive plans for fiscal 2023: Stock Options Restricted Stock Units Total (1) Weighted Restricted (4) Weighted (Shares in thousands) Outstanding at September 30, 2022 1,574 $ 49.89 1,012 $ 48.95 Granted 157 $ 73.84 225 $ 73.68 Performance-based adjustment (2) — $ — $ 20 $ 51.88 Exercised / Vested ( 75 ) $ 47.77 ( 275 ) $ 50.43 Cancelled / Forfeited ( 15 ) $ 49.88 ( 44 ) $ 50.20 Outstanding at September 30, 2023 (3) 1,641 $ 52.27 938 $ 54.45 Exercisable at September 30, 2023 1,172 $ 50.02 (1) Unvested stock options were approximately 469,000 a nd 651,000 at September 30, 2023 and 2022 and their weighted average grant date fair values were $ 57.92 and $ 49.30 , respectively. (2) Represents the net incremental number of shares issuable upon vesting of performance-based restricted stock units based on the Company’s actual financial performance metrics for fiscal 2023. (3) Stock options outstanding include options vested and expected to vest in the future and have a weighted average remaining contractual life of 6.13 years. (4) The number granted represents the number of shares issuable upon vesting of time-based restricted stock units and performance-based restricted stock units, assuming the Company performs at the target performance level in each year of the three-year performance period.
Weighted-Average Assumptions	The fair values on the grant date were calculated using the following weighted-average assumptions: Years Ended September 30 2023 2022 2021 Expected stock price volatility 38 % 35 % 36 % Risk free interest rate 4.0 % 1.4 % 0.6 % Expected life of options (years) 6 6 6 Expected annual dividends per year $ 1.48 $ 1.40 $ 1.40

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Changes in Each Component of AOCI, Net of Tax	Changes in each component of AOCI, net of tax, are as follows for fiscal 2023 and 2022: Currency Pension and Other Total (In millions) Balance at September 30, 2021 attributable to $ ( 265 ) $ ( 24 ) $ ( 289 ) Other comprehensive income (loss) before reclassifications ( 208 ) 12 ( 196 ) Amounts reclassified from AOCI 29 2 31 Less: Other comprehensive income (loss) attributable to ( 15 ) — ( 15 ) Balance at September 30, 2022 attributable to ( 429 ) ( 10 ) ( 439 ) Other comprehensive income (loss) before reclassifications 80 3 83 Amounts reclassified from AOCI ( 4 ) ( 2 ) ( 6 ) Less: Other comprehensive income (loss) attributable to — — — Balance at September 30, 2023 attributable to $ ( 353 ) $ ( 9 ) $ ( 362 )
Amounts Reclassified Out of AOCI	The amounts reclassified out of AOCI and into the Consolidated Statements of Operations for fiscal 2023, 2022 and 2021 are as follows: Affected Line Item in the Consolidated Years Ended September 30 Statements of Operations 2023 2022 2021 (In Millions) Derivatives: net investment hedges (Gains) losses reclassified to interest Interest expense $ ( 6 ) $ ( 6 ) $ ( 5 ) (Gains) losses excluded from effectiveness Interest expense 2 2 2 Release of current translation adjustment Loss on sale of business and asset impairment charge — 33 — Pension and other postretirement benefit Release of actuarial losses and prior service cost Loss on sale of business and asset impairment charge — 2 — Amortization of actuarial losses and prior service Other income (expense) ( 2 ) 1 3 Settlement and curtailment loss (gain) Other income (expense) — ( 1 ) 5 Total before tax $ ( 6 ) $ 31 $ 5

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Components of Basic and Diluted Earnings Per Common Share (EPS)	The following tables summarize the components of the basic and diluted earnings per common share (“EPS”) computations: Years Ended September 30 2023 2022 2021 (In millions, except per share amounts) Basic EPS: Net income (loss) attributable to Cabot Corporation $ 445 $ 209 $ 250 Less: Dividends and dividend equivalents to participating 1 1 1 Less: Undistributed earnings allocated to participating (1) 7 2 2 Earnings (loss) allocated to common shareholders (numerator) $ 437 $ 206 $ 247 Weighted average common shares and participating 57.3 57.4 57.5 Less: Participating securities (1) 1.2 0.9 0.8 Adjusted weighted average common shares 56.1 56.5 56.7 Per share amounts—basic: Net income (loss) attributable to Cabot Corporation $ 7.79 $ 3.65 $ 4.35 Diluted EPS: Earnings (loss) allocated to common shareholders $ 437 $ 206 $ 247 Plus: Earnings allocated to participating securities 8 3 3 Less: Adjusted earnings allocated to participating (2) 8 3 3 Earnings (loss) available to common shares (numerator) $ 437 $ 206 $ 247 Adjusted weighted average common shares outstanding 56.1 56.5 56.7 Effect of dilutive securities: Common shares issuable (3) 0.4 0.4 0.1 Adjusted weighted average common shares 56.5 56.9 56.8 Per share amounts—diluted: Net income (loss) attributable to Cabot Corporation $ 7.73 $ 3.62 $ 4.34 (1) Participating securities consist of shares underlying unvested time-based restricted stock units (the "TSUs"), earned and unvested performance-based restricted stock units (the "PSUs", and referred to in this note collectively with the TSUs as the "RSUs"), stock units accounted for under the Supplemental 401(k) Plan portion of the Company’s Deferred Compensation and Supplemental Retirement Plan, and stock units and phantom stock units accounted for under the Company’s Non-Employee Directors’ Deferral Plan. The holders of RSUs are entitled to receive dividend equivalents, payable in cash, to the extent dividends are paid on the outstanding shares of Common Stock, and equal in value to the dividends that would have been paid in respect of the Common Stock underlying the RSU. The accounts of holders of stock units and phantom stock units are credited with dividend equivalents, which are payable, in stock or cash, as the case may be, with the distribution of account balances .
Calculation of Undistributed Earnings	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: Years Ended September 30 2023 2022 2021 (In millions) Calculation of undistributed earnings: Net income (loss) attributable to Cabot Corporation $ 445 $ 209 $ 250 Less: Dividends declared on common stock 87 84 80 Less: Dividends and dividend equivalents to participating 1 1 1 Undistributed earnings (loss) $ 357 $ 124 $ 169 Allocation of undistributed earnings: Undistributed earnings (loss) allocated to common $ 350 $ 122 $ 167 Undistributed earnings allocated to participating 7 2 2 Undistributed earnings (loss) $ 357 $ 124 $ 169 (2) Undistributed earnings (loss) are adjusted for the assumed conversion of dilutive securities, which are described in (3) below, to common shares and then reallocated to participating securities. Represents incremental shares of common stock from the assumed exercise of stock options issued under Cabot’s equity incentive plans. For fiscal 2023, 2022 and 2021, respectively, 138,966 , 214,180 and 525,131 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.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Before Income Taxes	Income from operations before income taxes and equity in net earnings of affiliated companies was as follows: Years Ended September 30 2023 2022 2021 (In millions) Domestic $ 65 $ ( 20 ) $ ( 73 ) Foreign 386 355 479 Income from operations before income taxes and $ 451 $ 335 $ 406
Provision (Benefit) for Income Taxes	Tax provision (benefit) for income taxes consisted of the following: Years Ended September 30 2023 2022 2021 (In millions) U.S. federal and state: Current $ 5 $ 7 $ 11 Deferred ( 156 ) 2 ( 1 ) Total ( 151 ) 9 10 Foreign: Current 123 135 103 Deferred — ( 42 ) 10 Total 123 93 113 Provision (benefit) for income taxes $ ( 28 ) $ 102 $ 123
Reconciliation Using U.S. Statutory Rate	The provision ( benefit ) for income taxes differed from the provision for income taxes as calculated using the U.S. statutory rate as follows: Years Ended September 30 2023 2022 2021 (In millions) Computed tax expense at the federal statutory rate $ 95 $ 70 $ 85 Foreign impact of taxation at different rates, repatriation, 30 38 8 Global Intangible Low Taxed Income (GILTI) 15 23 18 Purification Solutions business divestiture — ( 179 ) — Impact of the Coronavirus Aid, Relief, and Economic — — 10 Impact of increase (decrease) in valuation allowance on ( 156 ) 160 ( 1 ) U.S. and state benefits from research and experimentation ( 2 ) ( 2 ) ( 2 ) Provision (settlement) of unrecognized tax benefits 2 1 1 Permanent differences, net ( 4 ) 10 7 State taxes, net of federal effect ( 8 ) ( 19 ) ( 3 ) Provision (benefit) for income taxes $ ( 28 ) $ 102 $ 123
Components of Deferred Income Taxes	Significant components of deferred income taxes were as follows: September 30 2023 2022 (In millions) Deferred tax assets: Deferred expenses $ 50 $ 10 Intangible assets 42 39 Inventory 14 15 Operating lease liability 22 21 Other 6 32 U.S. federal interest expense carryforward 42 33 Pension and other benefits 24 29 Net operating loss carryforwards 244 224 Capital loss carryforwards 132 137 Foreign tax credit carryforwards 68 55 R&D credit carryforwards 49 47 Other business credit carryforwards 19 20 Subtotal 712 662 Valuation allowance ( 498 ) ( 580 ) Total deferred tax assets $ 214 $ 82 September 30 2023 2022 (In millions) Deferred tax liabilities: Property, plant and equipment $ ( 47 ) $ ( 59 ) Right of use asset ( 22 ) ( 21 ) Unremitted earnings of non-U.S. subsidiaries ( 15 ) ( 22 ) Total deferred tax liabilities $ ( 84 ) $ ( 102 )
Expiration Dates of NOLs, Capital Loss and Other Tax Credit Carryforwards Before Valuation Allowances	The following table provides detail surrounding the expiration dates of NOLs, capital loss and other tax credit carryforwards before valuation allowances: Years Ending September 30 NOLs/Capital Losses Credits (In millions) 2024 - 2030 $ 1,051 $ 31 2031 and thereafter 268 103 Indefinite carryforwards 793 2 Total $ 2,112 $ 136
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits for fiscal 2023, 2022 and 2021 is as follows: Years Ended September 30 2023 2022 2021 (In millions) Balance at beginning of the year $ 159 $ 21 $ 23 Additions based on tax positions related to the current 1 138 1 Additions for tax positions of prior years — 2 — Reductions of tax positions of prior years ( 137 ) ( 1 ) ( 2 ) Reductions related to settlements ( 2 ) — — Reductions from lapse of statute of limitations ( 1 ) ( 1 ) ( 1 ) Balance at end of the year $ 20 $ 159 $ 21

Leases (Tables)

Leases (Tables)	12 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Components of Company's Lease Costs	The components of the Company’s lease costs were as follows: Years Ended September 30 2023 2022 2021 (In millions) Operating lease cost $ 26 $ 23 $ 25 Finance lease cost 6 6 7 Total lease cost $ 32 $ 29 $ 32
Supplemental Cash Flow Information Related to Company's Leases	Supplemental cash flow information related to the Company’s leases was as follows: Years Ended September 30 2023 2022 2021 (In millions) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 18 $ 17 $ 20 Operating cash flows from finance leases 2 2 2 Financing cash flows from finance leases 3 4 3 Right-of-use assets obtained in exchange for new operating lease liabilities $ 11 $ 14 $ 6 Right-of-use assets obtained in exchange for new finance lease liabilities $ 4 $ 1 $ 4
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 September 30, 2023 September 30, 2022 (In millions) Lease ROU assets: Operating Other assets $ 101 $ 96 Finance Net property, plant and equipment 39 41 Total lease ROU assets $ 140 $ 137 Lease liabilities: Current: Operating Accounts payable and accrued liabilities $ 15 $ 14 Finance Current portion of long-term debt 4 3 Long-term: Operating Other liabilities 84 83 Finance Long-term debt 24 26 Total lease liabilities $ 127 $ 126
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: Description September 30, 2023 September 30, 2022 Weighted-average remaining lease term (years): Operating leases 15 15 Finance leases 9 10 Weighted-average discount rate: Operating leases 3.28 % 2.97 % Finance leases 5.38 % 5.40 %
Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases	Future minimum lease payments under non-cancelable operating and finance leases as of September 30, 2023 were as follows: Years Ended September 30 Operating leases Finance leases (In millions) 2024 $ 18 $ 5 2025 16 4 2026 13 4 2027 12 3 2028 10 3 2029 and thereafter 51 15 Total lease payments 120 34 Less: imputed interest 21 6 Total $ 99 $ 28

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Components of Purchase Commitments	For these purchase commitments, the amounts included in the table below are based on market prices as of September 30, 2023 which may differ from actual market prices at the time of purchase. Payments Due by Fiscal Year 2024 2025 2026 2027 2028 Thereafter Total (In millions) Reinforcement Materials $ 208 $ 185 $ 181 $ 161 $ 101 $ 1,266 $ 2,102 Performance Chemicals 41 38 36 36 21 211 $ 383 Total $ 249 $ 223 $ 217 $ 197 $ 122 $ 1,477 $ 2,485

Financial Information by Segm_2

Financial Information by Segment & Geographic Area (Tables)	12 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Financial Information by Reportable Segment	Financial information by reportable segment is as follows: Years Ended September 30 Reinforcement Performance Purification (1) Segment Unallocated (2) Consolidated (In millions) 2023 Revenues from external customers (4) $ 2,563 $ 1,225 $ — $ 3,788 $ 143 $ 3,931 Depreciation and amortization $ 70 $ 72 $ — $ 142 $ 2 $ 144 Equity in earnings of affiliated companies $ 2 $ 3 $ — $ 5 $ — $ 5 Income (loss) from operations (5) $ 482 $ 125 $ — $ 607 $ ( 156 ) $ 451 Assets (6) $ 1,632 $ 1,473 $ — $ 3,105 $ 499 $ 3,604 Total expenditures for additions to long-lived (7) $ 149 $ 108 $ — $ 257 $ 8 $ 265 2022 Revenues from external customers (3)(4) $ 2,673 $ 1,388 $ 97 $ 4,158 $ 163 $ 4,321 Depreciation and amortization $ 70 $ 72 $ 3 $ 145 $ 1 $ 146 Equity in earnings of affiliated companies $ 4 $ 5 $ 1 $ 10 $ — $ 10 Income (loss) from operations (5) $ 408 $ 234 $ — $ 642 $ ( 307 ) $ 335 Assets (6) $ 1,691 $ 1,458 $ — $ 3,149 $ 376 $ 3,525 Total expenditures for additions to long-lived (7) $ 114 $ 100 $ 3 $ 217 $ 4 $ 221 2021 Revenues from external customers (3)(4) $ 1,838 $ 1,156 $ 257 $ 3,251 $ 158 $ 3,409 Depreciation and amortization $ 70 $ 73 $ 16 $ 159 $ 1 $ 160 Equity in earnings of affiliated companies $ — $ 2 $ 2 $ 4 $ ( 1 ) $ 3 Income (loss) from operations (5) $ 329 $ 211 $ 10 $ 550 $ ( 144 ) $ 406 Assets (6) $ 1,421 $ 1,325 $ 283 $ 3,029 $ 277 $ 3,306 Total expenditures for additions to long-lived (7) $ 104 $ 80 $ 9 $ 193 $ 5 $ 198 (1) Cabot divested its Purification Solutions business on March 1, 2022. Refer to Note D for the terms of this transaction. (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) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation. The allocation of such revenue resulted in an increase of $ 98 million and $ 57 million in the Reinforcement Materials segment and $ 16 million and $ 8 million in the Performance Chemicals segment, with an offsetting decrease in Unallocated and Other revenue for fiscal 2022 and fiscal 2021, respectively. There was no impact to Consolidated Total Revenue from external customers. (4) 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 are summarized as follows: Years Ended September 30 2023 2022 2021 (In millions) Shipping and handling fees $ 132 $ 162 $ 153 By-product sales 5 8 8 Other 6 ( 7 ) ( 3 ) Total $ 143 $ 163 $ 158 (5) Consolidated Total Income (loss) from operations before income taxes reconciles to Income (loss) from operations before income taxes and equity in earnings of affiliated companies on the Consolidated Statements of Operations. Total Income (loss) from operations before income taxes that are categorized as Unallocated and Other includes: Years Ended September 30 2023 2022 2021 (In millions) Interest expense $ ( 90 ) $ ( 56 ) $ ( 49 ) Certain items: (a) Gain on sale of land 1 17 — Legal and environmental matters and reserves (Note S) ( 10 ) ( 9 ) ( 25 ) Argentina controlled currency devaluation loss ( 7 ) — — Acquisition and integration-related charges ( 4 ) ( 6 ) ( 5 ) Global restructuring activities ( 4 ) ( 3 ) ( 11 ) Loss on sale of business and asset impairment charge ( 3 ) ( 207 ) — Other certain items ( 2 ) — ( 1 ) Gain on bargain purchase of a business (Note C) — 24 — Specialty Fluids divestiture related benefit — 5 — Employee benefit plan settlement and other charges — 1 ( 4 ) Purification Solutions divestiture related charges — ( 5 ) — Indirect tax settlement credits — — 12 Total certain items, pre-tax ( 29 ) ( 183 ) ( 34 ) Unallocated corporate costs (b) ( 54 ) ( 59 ) ( 58 ) General unallocated income (expense) (c) 22 1 — Less: Equity in earnings of affiliated companies, net of tax (d) 5 10 3 Total $ ( 156 ) $ ( 307 ) $ ( 144 ) (a) Certain items are items that management does not consider representative of operating segment results and they are, therefore, excluded from Segment EBIT. (b) Unallocated corporate costs 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, and unrealized holding gains (losses) for investments. (d) Equity in earnings of affiliated companies, net of tax is included in Segment EBIT and is removed from Unallocated and other to reconcile to income (loss) from operations before taxes and equity in earnings from affiliated companies. (6) Unallocated and Other assets include cash, marketable securities, cost investments, income taxes receivable, deferred taxes, headquarters’ assets and current and non-current assets held for sale. (7) Expenditures for additions to long-lived assets include total equity and other investments (including available-for-sale securities) and property, plant and equipment.
Revenue from External Customers and Property, Plant and Equipment Information by Geographic Area	Revenues from external customers attributable to an individual country, other than the U.S. and China, were not material for disclosure. Revenues from external customers by individual country are summarized as follows: Years Ended September 30 2023 2022 2021 (In millions) United States $ 738 $ 842 $ 668 China 972 1,129 858 Other countries 2,221 2,350 1,883 Total $ 3,931 $ 4,321 $ 3,409 Property, plant and equipment attributable to an individual country, other than the U.S. and China, were not material for disclosure. Property, plant and equipment information by individual country is summarized as follows: Years Ended September 30 2023 2022 (In millions) United States $ 588 $ 524 China 356 333 Other countries 468 413 Total $ 1,412 $ 1,270
Revenues from External Customers by Geographic Region	Each of the Company’s segments operates globally. In addition to presenting Revenue from external customers by reportable segment, the following tables further disaggregate Revenue from external customers by geographic region. Year Ended September 30, 2023 Reinforcement Performance Purification Consolidated Total (In millions) Americas $ 1,046 $ 379 $ — $ 1,425 Asia Pacific 995 491 — 1,486 Europe, Middle East and Africa 522 355 — 877 Segment revenues from external customers 2,563 1,225 — 3,788 Unallocated and other 143 Net sales and other operating revenues $ 3,931 Year Ended September 30, 2022 Reinforcement (1) Performance (1) Purification Consolidated Total (In millions) Americas $ 1,072 $ 419 $ 43 $ 1,534 Asia Pacific 1,049 567 14 1,630 Europe, Middle East and Africa 552 402 40 994 Segment revenues from external customers 2,673 1,388 97 4,158 Unallocated and other 163 Net sales and other operating revenues $ 4,321 (1) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation. Year Ended September 30, 2021 Reinforcement (1) Performance (1) Purification Consolidated Total (In millions) Americas $ 708 $ 311 $ 110 $ 1,129 Asia Pacific 777 489 34 $ 1,300 Europe, Middle East and Africa 353 356 113 822 Segment revenues from external customers 1,838 1,156 257 3,251 Unallocated and other 158 Net sales and other operating revenues $ 3,409 (1) Beginning in fiscal 2023, the Company began allocating energy center revenue to the applicable segment’s revenue. The Company recast prior period financial information to conform to the new presentation.

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Significant Accounting Policies [Line Items]
Equity affiliate investments	$ 20,000,000	$ 20,000,000
Capitalized interest	6,000,000	3,000,000	$ 1,000,000
Asset retirement obligation reserve	11,000,000	10,000,000
Changes in allowance	$ 0	0	0
Chance of utilizing the associated benefit for valuation allowances, maximum	50%
Equity Method Investments [Member]
Significant Accounting Policies [Line Items]
Dividends declared	$ 2,000,000	1,000,000	5,000,000
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
Minimum [Member] | Cabot [Member] | Equity Affiliate Investments [Member]
Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	20%
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
Maximum [Member] | Cabot [Member] | Equity Affiliate Investments [Member]
Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50%
Other Nonoperating Income (Expense) [Member]
Significant Accounting Policies [Line Items]
Foreign currency transaction gain (loss)	$ (35,000,000)	$ (13,000,000)	$ (6,000,000)

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
	Feb. 28, 2022	Sep. 30, 2022
Business Acquisition [Line Items]
Businesses acquisition, net of cash acquired		$ 9
Gain on bargain purchase of a business		24
Tokai Carbon Group Tianjin Co
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 9
Business acquisition, cash consideration	14
Businesses acquisition, net of cash acquired	$ 5
Tokai Carbon Group Tianjin Co | Accounts Payable and Accrued Liabilities [Member]
Business Acquisition [Line Items]
Gain on bargain purchase of a business		$ 24
Tokai Carbon Group Tianjin Co | Tokai Carbon's Registered Capital [Member]
Business Acquisition [Line Items]
Business acquisition, ownership percentage	100%

Divestitures - Additional Infor

Divestitures - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of business		$ 6	$ 79
Impairment charge		3	207
Purification Solutions [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment charge			197
Pre-tax loss on sale			$ 10
Additional pre-tax loss on sale of business		$ 3
One Equity Partners [Member] | Purification Solutions [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from sale of business	$ 85
Proceeds from divestiture of cash transferred	$ 7

Inventories - Components of Com

Inventories - Components of Company's Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 148	$ 182
Finished goods	374	427
Other	63	55
Total	$ 585	$ 664

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Inventory Disclosure [Abstract]
Obsolete inventory reserve	$ 14	$ 9

Property, Plant and Equipment -

Property, Plant and Equipment - Components of Property, Plant and Equipment (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Property Plant And Equipment [Abstract]
Land and land improvements	$ 72	$ 75
Buildings	576	553
Machinery and equipment	2,622	2,473
Other	228	229
Construction in progress	329	224
Total property, plant and equipment	3,827	3,554
Less: Accumulated depreciation	(2,415)	(2,284)
Net property, plant and equipment	$ 1,412	$ 1,270

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Depreciation expense	$ 138	$ 140	$ 152

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 129
Foreign currency impact	5
Ending balance	134
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	46
Foreign currency impact	5
Ending balance	51
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	83
Ending balance	$ 83

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Intangible Assets with Finite Lives (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 101	$ 95
Accumulated Amortization	(41)	(32)
Net Intangible Assets, finite lives	60	63
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	34	34
Accumulated Amortization	(10)	(8)
Net Intangible Assets, finite lives	24	26
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	2	2
Accumulated Amortization	(1)	(1)
Net Intangible Assets, finite lives	1	1
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	65	59
Accumulated Amortization	(30)	(23)
Net Intangible Assets, finite lives	$ 35	$ 36

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Goodwill And Intangible Assets [Line Items]
Amortization expense estimated for year one	$ 6
Amortization expense estimated for year two	6
Amortization expense estimated for year three	6
Amortization expense estimated for year four	6
Amortization expense estimated for year five	6
Cost of Sales, Selling and Administrative Expenses and Research and Technical Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ 6	$ 6	$ 8
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	17 years

Accounts Payable, Accrued Lia_3

Accounts Payable, Accrued Liabilities and Other Liabilities - Components of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Payables and Accruals [Abstract]
Accounts payable	$ 438	$ 533
Accrued employee compensation	55	66
Other accrued liabilities	107	108
Total	$ 600	$ 707

Accounts Payable, Accrued Lia_4

Accounts Payable, Accrued Liabilities and Other Liabilities - Components of Other Long-Term Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Payables and Accruals [Abstract]
Employee benefit plan liabilities	$ 48	$ 51
Operating lease liabilities	84	83
Other accrued liabilities	99	100
Total	$ 231	$ 234

Debt and Other Obligations - Ad

Debt and Other Obligations - Additional Information (Detail)	1 Months Ended					12 Months Ended
	Aug. 31, 2023	Jun. 30, 2022 USD ($)	Aug. 31, 2021 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	May 31, 2023 EUR (€)
Debt Instrument [Line Items]
Revolving credit facility, committed amount						$ 1,000,000,000
Short-term borrowings						174,000,000	$ 347,000,000
Revolving credit facility, cap amount used to calculate net debt						150,000,000
Long-term debt						1,082,000,000
Unsecured medium term notes outstanding issued						$ 8,000,000	8,000,000
Maturity of the total outstanding medium term notes, years						4 years
Weighted average interest of medium term notes						7.24%
Chinese Renminbi Debt [Member]
Debt Instrument [Line Items]
Long-term debt						$ 4,000,000	$ 4,000,000
3.4% Notes due fiscal 2026 [Member]
Debt Instrument [Line Items]
Debt maturity date						Sep. 15, 2026
Debt instrument, interest rate						3.40%	3.40%
Unsecured notes issued					$ 250,000,000
Debt instrument, discount					$ 1,000,000
Proceeds from issuance of unsecured notes						$ 248,000,000
Debt instrument due, year						2026	2026
3.4% Notes due fiscal 2026 [Member] | Fixed Rate Debt [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate					3.40%
Debt instrument due, year				2026
4.0% Notes due 2029 [Member]
Debt Instrument [Line Items]
Debt issuance cost				$ 3,000,000
Debt maturity date				Jul. 01, 2029
Debt instrument, interest rate				4%		4%	4%
Unsecured notes issued				$ 300,000,000
Debt instrument, discount				1,000,000
Proceeds from issuance of unsecured notes				$ 296,000,000
Debt instrument due, year				2029		2029	2029
5.0% Notes due fiscal 2032 [Member]
Debt Instrument [Line Items]
Debt issuance cost		$ 3,000,000
Debt maturity date		Jun. 30, 2032
Debt instrument, interest rate		5%				5%	5%
Unsecured notes issued		$ 400,000,000
Debt instrument, discount		3,000,000
Proceeds from issuance of unsecured notes		$ 394,000,000
Debt instrument due, year		2032				2032	2032
Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, covenant, ratio of consolidated total debt to consolidated EBITDA						3.50%
Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, covenant, ratio of consolidated total debt to consolidated EBITDA						1%
Revolving Credit Facility, expires fiscal 2027 [Member]
Debt Instrument [Line Items]
Revolving credit facility, committed amount			$ 1,000,000,000
Debt instrument, maturity date			Aug. 31, 2027
Amount available under credit facility						$ 828,000,000
Line of credit facility, commitment fee percentage	0.01%
Line of credit facility, interest rate during period	0.05%
Debt instrument due, year						2027	2027
Revolving Credit Facility - Euro, expires fiscal 2027 [Member]
Debt Instrument [Line Items]
Revolving credit facility, committed amount | €								€ 300,000,000
Debt instrument, maturity date						Aug. 31, 2027
Revolving credit facility, weighted average interest rate						4.82%
Credit agreement, available borrowing						$ 197,000,000
Debt issuance cost						$ 1,000,000
Debt instrument due, year						2027	2027
Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Debt instrument due, year						2024
Standby letters of credit, outstanding amount						$ 7,000,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Short-term borrowings						$ 172,000,000	$ 322,000,000
Weighted-average interest rate						5.44%	3.35%

Debt and Other Obligations - Sc

Debt and Other Obligations - Schedule of Long-Term Obligations (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Total variable rate debt	$ 120	$ 114
Medium Term Notes	8	8
Debt	1,082
Total debt	962	962
Finance lease obligations (Note R)	28	29
Unamortized debt issuance costs and debt discount	(8)	(9)
Total debt	1,102	1,096
Less current portion of long-term debt	(8)	(7)
Total long-term debt	1,094	1,089
Revolving Credit Facility - Euro, expires fiscal 2027 [Member]
Debt Instrument [Line Items]
Line of credit	120	114
3.4% Notes due fiscal 2026 [Member]
Debt Instrument [Line Items]
Notes	250	250
4.0% Notes due fiscal 2029 [Member]
Debt Instrument [Line Items]
Notes	300	300
5.0% Notes due fiscal 2032 [Member]
Debt Instrument [Line Items]
Notes	400	400
Medium Term Notes due fiscal 2028, 6.57% - 7.28% [Member]
Debt Instrument [Line Items]
Medium Term Notes	8	8
Chinese Renminbi Debt, Due Fiscal 2024, 4.3% [Member]
Debt Instrument [Line Items]
Debt	$ 4	$ 4

Debt and Other Obligations - _2

Debt and Other Obligations - Schedule of Long-Term Obligations (Parenthetical) (Detail)	1 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2019	Sep. 30, 2023	Sep. 30, 2022
Revolving Credit Facility, expires fiscal 2027 [Member]
Debt Instrument [Line Items]
Debt instrument due, year			2027	2027
Revolving Credit Facility - Euro, expires fiscal 2027 [Member]
Debt Instrument [Line Items]
Debt instrument due, year			2027	2027
3.4% Notes due fiscal 2026 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			3.40%	3.40%
Debt instrument due, year			2026	2026
4.0% Notes due 2029 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		4%	4%	4%
Debt instrument due, year		2029	2029	2029
5.0% Notes due fiscal 2032 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	5%		5%	5%
Debt instrument due, year	2032		2032	2032
Medium Term Notes due fiscal 2028, 6.57% - 7.28% [Member]
Debt Instrument [Line Items]
Debt instrument due, year			2028	2028
Medium Term Notes due fiscal 2028, 6.57% - 7.28% [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			6.57%	6.57%
Medium Term Notes due fiscal 2028, 6.57% - 7.28% [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			7.28%	7.28%
Chinese Renminbi Debt, Due Fiscal 2024, 4.3% [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			4.30%	4.30%
Debt instrument due, year			2024	2024

Debt and Other Obligations - _3

Debt and Other Obligations - Schedule of Future Years Payment (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Debt Disclosure [Abstract]
2024	$ 4
2026	250
2027	120
2028	8
Thereafter	700
Total	$ 1,082

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
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	1,040,000,000	1,060,000,000
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	8,000,000	8,000,000
Fixed Rate Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt	$ 1,080,000,000	$ 1,080,000,000

Derivatives - Additional Inform

Derivatives - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Derivative [Line Items]
Significant concentration of credit risk associated with our derivative instruments	$ 0	$ 0
Maximum [Member]
Derivative [Line Items]
Fair value of derivative instruments not designated as hedges, liability	1,000,000	1,000,000
Net Investment Hedge [Member] | Cross Currency Swaps [Member]
Derivative [Line Items]
Net cash interest received	4,000,000	4,000,000	$ 3,000,000
Fair value of swaps, net asset	12,000,000	29,000,000
Cumulative gain related to swaps	$ 15,000,000	$ 32,000,000
Net Investment Hedge [Member] | Cross Currency Swaps [Member] | Fixed Rate Debt [Member]
Derivative [Line Items]
Derivative Instruments Frequency of Cash Settlements	semi-annually

Derivatives - Details of Deriva

Derivatives - Details of Derivatives Held to Manage Foreign Currency Risk (Detail)		Sep. 30, 2023 USD ($)	Sep. 30, 2023 EUR (€)	Sep. 30, 2022 USD ($)	Sep. 30, 2022 EUR (€)	Sep. 30, 2016
3.4% Notes [Member]
Derivative [Line Items]
Interest rate on borrowing		3.40%	3.40%	3.40%	3.40%
3.4% Notes [Member] | Fixed Rate Debt [Member]
Derivative [Line Items]
Interest rate on borrowing						3.40%
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%	3.40%	3.40%	3.40%
Not Designated as Hedging Instrument [Member] | Forward Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional Amount	[1]	$ 82,000,000		$ 42,000,000
[1] At September 30, 2023, the Company’s forward foreign exchange contracts were denominated in Indonesian rupiah, Czech koruna, and Colombian peso. At September 30, 2022, the Company’s forward foreign exchange contracts were denominated in Indonesian rupiah and Czech koruna.

Derivatives - Summary Impact of

Derivatives - Summary Impact of Cross-currency Swaps to AOCI and Consolidated Statements of Operations (Detail) - Cross Currency Swaps [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) Recognized in AOCI	$ (13)	$ 30	$ 7
(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations	$ (6)	$ (6)	$ (5)
Derivative Instrument, Gain (Loss) Reclassified from AOCI into Income, Effective Portion, Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest Expense	Interest Expense	Interest Expense
(Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing)	$ 2	$ 2	$ 2

Insurance Recoveries - Addition

Insurance Recoveries - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Business Interruption Loss [Line Items]
Cash provided by investing activities	$ 12	$ 1	$ 2
Gain Recognized Rrelated to lost margin and replacement of fixed assets	9
Pepinster, Belgium [Member]
Business Interruption Loss [Line Items]
Insurance proceeds	14	11	8
Pepinster, Belgium [Member] | Flood [Member]
Business Interruption Loss [Line Items]
Flood-related expenses	0	6	17
Insurance proceeds	33
Cash provided by operating activities	2	10	6
Cash provided by investing activities	$ 12	1	$ 2
Franklin, Louisiana [Member] | Equipment Failure [Member]
Business Interruption Loss [Line Items]
Insurance proceeds		$ 8

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plans expenses		$ 19	$ 15	$ 18
Pension Benefits [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contribution	$ 4
Postretirement Benefits [Member] | Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Postretirement medical benefits	$ 3
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation		2	2
Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation		$ 131	$ 125
Foreign Plans [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of weighted-average target asset allocation		29%
Foreign Plans [Member] | Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of weighted-average target asset allocation		46%
Foreign Plans [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of weighted-average target asset allocation		18%
Foreign Plans [Member] | Cash and Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of weighted-average target asset allocation		7%

Employee Benefit Plans - Change

Employee Benefit Plans - Change in Projected Benefit Obligations and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Change in Plan Assets:
Fair value of plan assets at beginning of year	$ 135
Fair value of plan assets at end of year	144	$ 135
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	$ 2	3
(Gain) loss from changes in actuarial assumptions and plan experience		$ (1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Benefit obligation at end of year	$ 2	$ 2	$ 3
Change in Plan Assets:
Funded status	(2)	(2)
Recognized asset (liability)	(2)	(2)
Pension Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	133	221
Service cost	3	4	6
Interest cost	$ 7	$ 4	3
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Plan participants’ contribution	$ 1	$ 1
Foreign currency exchange rate changes	6	(27)
(Gain) loss from changes in actuarial assumptions and plan experience	(4)	(43)
Benefits paid	(5)	(9)
Settlements or curtailments	$ (2)	$ (2)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Divestiture of a business		$ (16)
Benefit obligation at end of year	$ 139	133	221
Change in Plan Assets:
Fair value of plan assets at beginning of year	135	217
Actual return on plan assets	4	(35)
Employer contribution	4	5
Plan participants’ contribution	1	1
Foreign currency exchange rate changes	7	(24)
Benefits paid	(5)	(9)
Settlements or curtailments	(2)	(2)
Divestiture of a business		(18)
Fair value of plan assets at end of year	144	135	217
Funded status	5	2
Recognized asset (liability)	5	2
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	16	25
Interest cost	1
(Gain) loss from changes in actuarial assumptions and plan experience	(1)	(4)
Benefits paid	$ (2)	(3)
Settlements or curtailments		$ (2)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Benefit obligation at end of year	$ 14	$ 16	25
Change in Plan Assets:
Employer contribution	2	5
Benefits paid	(2)	(3)
Settlements or curtailments		(2)
Funded status	(14)	(16)
Recognized asset (liability)	(14)	(16)
Postretirement Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	13	19
Interest cost	$ 1	$ 1	1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Foreign currency exchange rate changes	$ 1	$ (2)
(Gain) loss from changes in actuarial assumptions and plan experience	(3)	(5)
Benefits paid	(1)
Benefit obligation at end of year	11	13	$ 19
Change in Plan Assets:
Employer contribution	1
Benefits paid	(1)
Funded status	(11)	(13)
Recognized asset (liability)	$ (11)	$ (13)

Employee Benefit Plans - Assump

Employee Benefit Plans - Assumptions Used to Determine Pension Benefit Obligations and Periodic Benefit Costs, Postretirement Benefit Obligations and Net Costs (Detail)		12 Months Ended
		Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate		6%		5.50%	2.20%
Initial health care cost trend rate				3%
Cash balance interest credit rate		2%		2%	2%
Discount rate - benefit obligation		5.60%		2.20%	2.50%
Discount rate - interest cost		5.30%		1.60%	1.40%
Cash balance interest credit rate		2%		2%	2.10%
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate		4.70%		4.50%	2.10%
Initial health care cost trend rate		3%		3%	2.90%
Cash balance interest credit rate		2.10%		2%	1.70%
Discount rate - benefit obligation		4.50%		2.10%	1.70%
Discount rate - service cost		3.60%		2%	1.70%
Discount rate - interest cost		4.50%		1.70%	1.40%
Expected long-term rate of return on plan assets		5.10%		3.50%	4.60%
Initial health care cost trend rate		3%		2.90%	3%
Cash balance interest credit rate		2%		1.70%	1.70%
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	[1]	6%		5.60%	2.40%
Initial health care cost trend rate		5%	[1]	0%	5.50%	[1]
Discount rate - benefit obligation	[1]	5.60%		2.40%	2.10%
Discount rate - service cost	[1]	5.40%		1.70%	1.50%
Discount rate - interest cost	[1]	5.30%		1.60%	1.40%
Initial health care cost trend rate	[1]			5.50%	6%
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	[1]	5.70%		5.10%	2.80%
Initial health care cost trend rate	[1]	6.40%		6.80%	6.90%
Discount rate - benefit obligation	[1]	5.10%		2.80%	2.40%
Discount rate - service cost	[1]	5.10%		3.50%	3%
Discount rate - interest cost	[1]	5.10%		2.50%	2.10%
Initial health care cost trend rate	[1]	6.80%		6.90%	6.90%
[1] The initial health care cost trend rate is set at 5 % for the 2023 U.S. plan assumptions as the 2024 Medicare Part B premiums are expected to increase. The trend rates for all future years beyond 2024 also reflect expected 5 % increases. The initial health care cost trend rate was set at zero for the 2022 U.S. plan assumptions in light of the expected downward adjustment the U.S. government was expected to make to the 2023 Medicare Part B premiums, however, all trend rates beyond the initial year were set to 5 %

Employee Benefit Plans - Assu_2

Employee Benefit Plans - Assumptions Used to Determine Pension Benefit Obligations and Periodic Benefit Costs, Postretirement Benefit Obligations and Net Costs (Parenthetical) (Detail)	Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2021
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Initial health care cost trend rate	5%	[1]	0%	5.50%	[1]
[1] The initial health care cost trend rate is set at 5 % for the 2023 U.S. plan assumptions as the 2024 Medicare Part B premiums are expected to increase. The trend rates for all future years beyond 2024 also reflect expected 5 % increases. The initial health care cost trend rate was set at zero for the 2022 U.S. plan assumptions in light of the expected downward adjustment the U.S. government was expected to make to the 2023 Medicare Part B premiums, however, all trend rates beyond the initial year were set to 5 %

Employee Benefit Plans - Amount

Employee Benefit Plans - Amounts Recognized in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other liabilities	$ (2)	$ (2)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	30	26
Accounts payable and accrued liabilities	(1)	(1)
Other liabilities	(24)	(23)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(2)	(2)
Other liabilities	(12)	(14)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accounts payable and accrued liabilities	(1)	(1)
Other liabilities	$ (10)	$ (12)

Employee Benefit Plans - Amou_2

Employee Benefit Plans - Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 24	$ 23
Net prior service credit	(1)	(1)
Balance in accumulated other comprehensive (income) loss, pretax	23	22
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(6)	(6)
Balance in accumulated other comprehensive (income) loss, pretax	(6)	(6)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	(7)	(4)
Balance in accumulated other comprehensive (income) loss, pretax	$ (7)	$ (4)

Employee Benefit Plans - Estima

Employee Benefit Plans - Estimated Future Benefit Payments (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2029 - 2033	$ 1
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2024	9
2025	9
2026	9
2027	11
2028	11
2029 - 2033	49
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2024	2
2025	2
2026	2
2027	2
2028	2
2029 - 2033	6
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
2024	1
2025	1
2026	1
2027	1
2028	1
2029 - 2033	$ 4

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Settlements or Curtailments cost			$ 4
Net periodic (benefit) cost			4
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 4	6
Interest cost	7	4	3
Expected return on plan assets	$ (7)	$ (6)	$ (10)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Amortization of net losses	$ (1)	$ 1	$ 3
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Settlements or Curtailments cost			$ 1
Other			2
Net periodic (benefit) cost	$ 2	$ 3	5
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1
Amortization of net losses	$ (1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Settlements or Curtailments cost		$ (1)
Net periodic (benefit) cost		(1)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 1	$ 1
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Net periodic (benefit) cost	$ 1	$ 1	$ 1

Employee Benefit Plans - Other

Employee Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss), Pre-Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses			$ (2)
(Loss) gain on settlements			(4)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Net changes recognized in Total other comprehensive (income) loss			(6)
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	$ 1	$ (2)	(15)
Prior service (credit) cost			(1)
Amortization of prior unrecognized loss	$ 1	(1)	(3)
Loss on divestiture		$ (2)
(Loss) gain on settlements			(1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Net changes recognized in Total other comprehensive (income) loss	$ 2	$ (5)	$ (20)
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	(1)	(4)
Amortization of prior unrecognized loss	1
(Loss) gain on settlements		1
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Other income (expense)
Net changes recognized in Total other comprehensive (income) loss		(3)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net (gains) losses	(3)	(4)	$ (2)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Other income (expense)
Net changes recognized in Total other comprehensive (income) loss	$ (3)	$ (4)	$ (2)

Employee Benefit Plans - Othe_2

Employee Benefit Plans - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss), Pre-Tax (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive (Income) Loss, pension and other postretirement tax benefit (provision)		$ 3	$ 8
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive (Income) Loss, pension and other postretirement tax benefit (provision)	$ (1)

Employee Benefit Plans - Define

Employee Benefit Plans - Defined Benefit Pension Plans Weighted-Average Asset Allocations (Detail) - Foreign Plans [Member]		Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Equity securities		19%	20%
Debt securities		31%	68%
Real estate		10%	7%
Cash and other securities	[1]	40%	5%
Total		100%	100%
[1] The asset allocation is temporarily changed as a result of the insurance contracts Cabot Carbon Limited Pension Plan and Carbon Plastics Pension Plan purchased with plan assets in anticipation of the settlement discussed above.

Employee Benefit Plans - Fair V

Employee Benefit Plans - Fair Value of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		$ 144	$ 135
Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		13	9
Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		78	120
Other Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets			1
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		53	5
Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		16	10
Fair Value, Inputs, Level 1 | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		12	8
Fair Value, Inputs, Level 1 | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		4	1
Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		128	125
Significant Observable Inputs (Level 2) [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	1
Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		74	119
Significant Observable Inputs (Level 2) [Member] | Other Investment Funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets			1
Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		53	5
Cash and Cash Equivalent Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets			1
Cash and Cash Equivalent Funds [Member] | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets			1
Non-U.S. Equities [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		6	4
Non-U.S. Equities [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		6	4
Equity Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[1]	21	23
Equity Funds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[1]	21	23
Non-U.S. Government Bonds [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		2	1
Non-U.S. Government Bonds [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		2	1
Fixed Income Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[2]	38	86
Fixed Income Funds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[2]	38	86
Non-U.S. Corporate Bonds [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		3	2
Non-U.S. Corporate Bonds [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		3	2
Real Estate [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[3]	15	9
Real Estate [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[3]	15	9
Mortgage Backed Securities [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	1
Mortgage Backed Securities [Member] | Significant Observable Inputs (Level 2) [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	1
Other Fixed Income [Member] | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	1
Other Fixed Income [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1	1
Cash Equivalent Funds [Member] | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		4	1
Cash Equivalent Funds [Member] | Fair Value, Inputs, Level 1 | Total Investment Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		4	1
Insurance Contracts [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[4]	52	5
Insurance Contracts [Member] | Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets	[4]	52	$ 5
Other Alternative Investments [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		1
Other Alternative Investments [Member] | Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets		$ 1
[1] The equity funds asset class includes funds that invest in U.S. equities as well as equity securities issued by companies incorporated, listed or domiciled in countries in developed and/or emerging markets. These companies may be in the small-, mid- or large-cap categories. The fixed income funds asset class includes investments in high quality funds. High quality fixed income funds primarily invest in low-risk U.S. and non-U.S. government securities, investment-grade corporate bonds, mortgages and asset-backed securities. A significant portion of the fixed income funds include investment in long-term bond funds. The real estate funds asset class includes funds that primarily invest in entities which are principally engaged in the ownership, acquisition, development, financing, sale and/or management of income-producing real estate properties, both commercial and residential. These funds typically seek long-term growth of capital and current income that is above average relative to public equity funds. Insurance contracts held by the Company’s non-U.S. plans are issued by well-known, highly rated insurance companies.

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Mar. 11, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting in first anniversary	30%
Percentage of vesting in second anniversary	30%
Percentage of vesting in third anniversary	40%
Net stock-based compensation expense	$ 18	$ 22	$ 20
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price equal to market price on the date of grant	100%
Vesting period (in years)	3 years
Expiration period, years	10 years
Unrecognized compensation cost	$ 3
Weighted-average period, years	1 year
Options outstanding, aggregate intrinsic value	$ 29
Options exercisable, aggregate intrinsic value	29
Intrinsic value of options exercised	2	4	2
Cash received from exercises	$ 4	$ 6	$ 5
Stock Options, Weighted Average Grant Date Fair Value, Granted	$ 26.28	$ 15.95	$ 9.69
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (in years)	3 years
Unrecognized compensation cost	$ 16
Weighted-average period, years	1 year
Estimated weighted average grant date fair value	$ 73.68	$ 58.72	$ 41.92
Intrinsic value of restricted stock units vested	$ 20	$ 13	$ 8
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period (in years)	3 years
Supplemental 401(k) Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Supplemental retirement savings plan, aggregate value of the accounts, shares	113,000	103,000
2017 Long-Term Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, authorized shares				8,625,000

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expenses (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense before tax	$ 20	$ 23	$ 21
Income tax benefit	(2)	(1)	(1)
Net stock-based compensation expense	18	22	20
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense before tax	2	3	2
Selling and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense before tax	16	18	17
Research and Technical Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense before tax	$ 2	$ 2	$ 2

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive Plan Activity (Detail) - $ / shares shares in Thousands		12 Months Ended
		Sep. 30, 2023		Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options, Total Options, Outstanding at September 30, 2022	[1]	1,574
Stock Options, Total Options, Granted	[1]	157
Stock Options, Total Options, Exercised / Vested	[1]	(75)
Stock Options, Total Options, Cancelled / Forfeited	[1]	(15)
Stock Options, Total Options, Outstanding at September 30, 2023	[1]	1,641	[2]	1,574
Stock Options, Total Options, Exercisable at September 30, 2023	[1]	1,172
Stock Options, Weighted Average Exercise Price, Outstanding at September 30, 2022		$ 49.89
Stock Options, Weighted Average Exercise Price, Granted		73.84
Stock Options, Weighted Average Exercise Price, Exercised / Vested		47.77
Stock Options, Weighted Average Exercise Price, Cancelled / Forfeited		49.88
Stock Options, Weighted Average Exercise Price, Outstanding at September 30, 2023		52.27	[2]	$ 49.89
Stock Options, Weighted Average Exercise Price, Exercisable at September 30, 2023		$ 50.02
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted Stock / Units, Outstanding at September 30, 2022	[3]	1,012
Restricted Stock / Units, Granted	[3]	225
Restricted Stock / Units, Performance-based adjustment	[3],[4]	20
Restricted Stock / Units, Exercised / Vested	[3]	(275)
Restricted Stock / Units, Cancelled / Forfeited	[3]	(44)
Restricted Stock / Units, Outstanding at September 30, 2023	[3]	938	[2]	1,012
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Outstanding at September 30, 2022		$ 48.95
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Granted		73.68		$ 58.72	$ 41.92
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Performance-based adjustment	[4]	51.88
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Exercised / Vested		50.43
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Cancelled / Forfeited		50.2
Restricted Stock / Units, Weighted Average Grant Date Fair Value, Outstanding at September 30, 2023		$ 54.45	[2]	$ 48.95
[1] Unvested stock options were approximately 469,000 a nd 651,000 at September 30, 2023 and 2022 and their weighted average grant date fair values were $ 57.92 and $ 49.30 , respectively. Stock options outstanding include options vested and expected to vest in the future and have a weighted average remaining contractual life of 6.13 years. The number granted represents the number of shares issuable upon vesting of time-based restricted stock units and performance-based restricted stock units, assuming the Company performs at the target performance level in each year of the three-year performance period. Represents the net incremental number of shares issuable upon vesting of performance-based restricted stock units based on the Company’s actual financial performance metrics for fiscal 2023.

Stock-Based Compensation - Eq_2

Stock-Based Compensation - Equity Incentive Plan Activity (Parenthetical) (Detail) - $ / shares shares in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Stock options outstanding include options vested and expected to vest in the future, weighted average remaining contractual life, in years	6 years 1 month 17 days
Unvested stock options	469,000	651,000
Unvested stock options, weighted average grant date fair value	$ 57.92	$ 49.3

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-Average Assumptions (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-Based Payment Arrangement [Abstract]
Expected stock price volatility	38%	35%	36%
Risk free interest rate	4%	1.40%	0.60%
Expected life of options (years)	6 years	6 years	6 years
Expected annual dividends per year	$ 1.48	$ 1.40	$ 1.40

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 1,032	$ 1,090
Ending Balance	1,407	1,032
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(429)	(265)
Other comprehensive income (loss) before reclassifications	80	(208)
Amounts reclassified from AOCI	(4)	29
Less: Other comprehensive income (loss) attributable to noncontrolling interests		(15)
Ending Balance	(353)	(429)
Pension and Other Postretirement Benefit Liability Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(10)	(24)
Other comprehensive income (loss) before reclassifications	3	12
Amounts reclassified from AOCI	(2)	2
Ending Balance	(9)	(10)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(439)	(289)
Other comprehensive income (loss) before reclassifications	83	(196)
Amounts reclassified from AOCI	(6)	31
Less: Other comprehensive income (loss) attributable to noncontrolling interests		(15)
Ending Balance	$ (362)	$ (439)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of AOCI (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (6)	$ 31	$ 5
(Gains) Losses Reclassified to Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(6)	(6)	(5)
(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	2	2	2
Release of Current Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		33
Release of Actuarial Losses and Prior Service Cost (Credit) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		2
Amortization of Actuarial Losses and Prior Service Cost (Credit) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (2)	1	3
Settlement and Curtailment Loss (Gain)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		$ (1)	$ 5

Earnings Per Share - Components

Earnings Per Share - Components of Basic and Diluted Earnings Per Common Share (EPS) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Basic EPS:
Net income (loss) attributable to Cabot Corporation	$ 445	$ 209	$ 250
Less: Dividends and dividend equivalents to participating securities	1	1	1
Less: Undistributed earnings allocated to participating securities	7	2	2
Earnings (loss) allocated to common shareholders (numerator)	$ 437	$ 206	$ 247
Weighted average common shares and participating securities outstanding	57.3	57.4	57.5
Less: Participating securities	1.2	0.9	0.8
Adjusted weighted average common shares (denominator)	56.1	56.5	56.7
Basic	$ 7.79	$ 3.65	$ 4.35
Diluted EPS:
Earnings (loss) allocated to common shareholders	$ 437	$ 206	$ 247
Plus: Earnings allocated to participating securities	8	3	3
Less: Adjusted earnings allocated to participating securities	8	3	3
Earnings (loss) available to common shares (numerator)	$ 437	$ 206	$ 247
Adjusted weighted average common shares outstanding	56.1	56.5	56.7
Common shares issuable	0.4	0.4	0.1
Adjusted weighted average common shares (denominator)	56.5	56.9	56.8
Diluted	$ 7.73	$ 3.62	$ 4.34

Earnings Per Share - Calculatio

Earnings Per Share - Calculation of Undistributed Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net income (loss) attributable to Cabot Corporation	$ 445	$ 209	$ 250
Less: Dividends declared on common stock	87	84	80
Less: Dividends and dividend equivalents to participating securities	1	1	1
Undistributed earnings (loss)	357	124	169
Undistributed earnings (loss) allocated to common shareholders	350	122	167
Undistributed earnings allocated to participating securities	$ 7	$ 2	$ 2

Earnings Per Share - Componen_2

Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Parenthetical) (Detail) - shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share	138,966	214,180	525,131

Income Taxes - Income Before In

Income Taxes - Income Before Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest [Abstract]
Domestic	$ 65	$ (20)	$ (73)
Foreign	386	355	479
Income (loss) from operations before income taxes and equity in earnings of affiliated companies	$ 451	$ 335	$ 406

Income Taxes - Provision (Benef

Income Taxes - Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
U.S. federal and state, Current	$ 5	$ 7	$ 11
U.S. federal and state, Deferred	(156)	2	(1)
U.S. federal and state, Total	(151)	9	10
Foreign, Current	123	135	103
Foreign, Deferred		(42)	10
Foreign, Total	123	93	113
Provision (benefit) for income taxes	$ (28)	$ 102	$ 123

Income Taxes - Reconciliation U

Income Taxes - Reconciliation Using U.S. Statutory Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Computed tax expense at the federal statutory rate	$ 95	$ 70	$ 85
Foreign impact of taxation at different rates, repatriation, valuation allowance, and other	30	38	8
Global Intangible Low Taxed Income (GILTI)	15	23	18
Purification Solutions business divestiture		(179)
Impact of the Coronavirus Aid, Relief, and Economic Security ("CARES") Act of 2020			10
Impact of increase (decrease) in valuation allowance on U.S. deferred taxes	(156)	160	(1)
U.S. and state benefits from research and experimentation activities	(2)	(2)	(2)
Provision (settlement) of unrecognized tax benefits	2	1	1
Permanent differences, net	(4)	10	7
State taxes, net of federal effect	(8)	(19)	(3)
Provision (benefit) for income taxes	$ (28)	$ 102	$ 123

Income Taxes - Components of De

Income Taxes - Components of Deferred Income Taxes (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Components of Deferred Tax Assets [Abstract]
Deferred expenses	$ 50	$ 10
Intangible assets	42	39
Inventory	14	15
Operating lease liability	22	21
Other	6	32
U.S. federal interest expense carryforward	42	33
Pension and other benefits	24	29
Net operating loss carryforwards	244	224
Capital loss carryforwards	132	137
Foreign tax credit carryforwards	68	55
R&D credit carryforwards	49	47
Other business credit carryforwards	19	20
Subtotal	712	662
Valuation allowance	(498)	(580)
Total deferred tax assets	214	82
Property, plant and equipment	(47)	(59)
Right of use asset	(22)	(21)
Unremitted earnings of non-U.S. subsidiaries	(15)	(22)
Total deferred tax liabilities	$ (84)	$ (102)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Income Taxes [Line Items]
Other tax credit carryforwards	$ 136,000,000
Undistributed earnings	1,359,000,000
Unrecognized tax benefits	20,000,000	$ 159,000,000	$ 21,000,000	$ 23,000,000
Unrecognized tax benefits, offset against deferred tax assets	14,000,000
Non cash income tax expense (benefit)	152,000,000
Accruals for penalties and interest	5,000,000
Total penalties and interest	2,000,000	2,000,000	1,000,000
Favorable impact on tax provision	$ 20,000,000
Earliest Tax Year [Member] | United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2020
Latest Tax Year [Member] | United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2022
Purification Solutions [Member]
Income Taxes [Line Items]
Income tax benefit from tax loss related to divestiture	$ 137,000,000	137,000,000
Other Liabilities [Member]
Income Taxes [Line Items]
Unrecognized tax benefits, recorded	6,000,000
Maximum [Member]
Income Taxes [Line Items]
Other tax credit carryforwards	1,000,000
Foreign Jurisdictions [Member]
Income Taxes [Line Items]
NOLs	$ 24,000,000
Foreign Jurisdictions [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2006
Foreign Jurisdictions [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2022
State Tax Authorities [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2010
State Tax Authorities [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2022
U.S. Defined Benefit Plans [Member]
Income Taxes [Line Items]
Increased/(decreased) valuation in allowance	$ (498,000,000)
U.S. Defined Benefit Plans [Member] | Maximum [Member]
Income Taxes [Line Items]
Increased/(decreased) valuation in allowance		580,000,000	470,000,000
U.S. Defined Benefit Plans [Member] | Minimum [Member]
Income Taxes [Line Items]
Increased/(decreased) valuation in allowance		$ (82,000,000)	$ 110,000,000

Income Taxes - Expiration Dates

Income Taxes - Expiration Dates of NOLs, Capital Loss and Other Tax Credit Carryforwards Before Valuation Allowances (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Significant Tax Attributes And Dates Of Expiration [Line Items]
NOLs/Capital Losses	$ 2,112
Credits	136
2024 - 2030 [Member]
Significant Tax Attributes And Dates Of Expiration [Line Items]
NOLs/Capital Losses	1,051
Credits	31
2031 and Thereafter [Member]
Significant Tax Attributes And Dates Of Expiration [Line Items]
NOLs/Capital Losses	268
Credits	103
Indefinite Carryforwards [Member]
Significant Tax Attributes And Dates Of Expiration [Line Items]
NOLs/Capital Losses	793
Credits	$ 2

Income Taxes - Expiration Dat_2

Income Taxes - Expiration Dates of NOLs, Capital Loss and Other Tax Credit Carryforwards Before Valuation Allowances (Parenthetical) (Detail)	12 Months Ended
	Sep. 30, 2023
Significant Tax Attributes And Dates Of Expiration [Line Items]
Expiration periods	2031
Minimum [Member]
Significant Tax Attributes And Dates Of Expiration [Line Items]
Expiration periods	2024
Maximum [Member]
Significant Tax Attributes And Dates Of Expiration [Line Items]
Expiration periods	2030

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Balance at beginning of the year	$ 159	$ 21	$ 23
Additions based on tax positions related to the current year	1	138	1
Additions for tax positions of prior years		2
Reductions of tax positions of prior years	(137)	(1)	(2)
Reductions related to settlements	(2)
Reductions from lapse of statute of limitations	(1)	(1)	(1)
Balance at end of the year	$ 20	$ 159	$ 21

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Lessee Lease Description [Line Items]
Short term lease costs	$ 7	$ 5	$ 5
Variable lease cost	$ 2	$ 1	$ 1
Minimum [Member]
Lessee Lease Description [Line Items]
Lease term	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lease term	16 years
Lease extension period	15 years
Maximum [Member] | Land [Member]
Lessee Lease Description [Line Items]
Lease term	79 years

Leases - Components of Company'

Leases - Components of Company's Lease Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating lease cost	$ 26	$ 23	$ 25
Finance lease cost	6	6	7
Total lease cost	$ 32	$ 29	$ 32

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information Related to Company's Leases (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 18	$ 17	$ 20
Operating cash flows from finance leases	2	2	2
Financing cash flows from finance leases	3	4	3
Right-of-use assets obtained in exchange for new operating lease liabilities	11	14	6
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 4	$ 1	$ 4

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information Related to Company's Leases (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Lease ROU assets:
Operating	$ 101	$ 96
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Finance	$ 39	$ 41
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Net property, plant and equipment	Net property, plant and equipment
Total lease ROU assets	$ 140	$ 137
Lease liabilities:
Operating	$ 15	$ 14
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accounts payable and accrued liabilities	Accounts payable and accrued liabilities
Finance	$ 4	$ 3
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Current portion of long-term debt	Current portion of long-term debt
Operating	$ 84	$ 83
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Finance	$ 24	$ 26
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Total lease liabilities	$ 127	$ 126

Leases - Weighed Average Remain

Leases - Weighed Average Remaining Lease Term and Discount Rates (Detail)	Sep. 30, 2023	Sep. 30, 2022
Lease, Cost [Abstract]
Operating leases	15 years	15 years
Finance leases	9 years	10 years
Operating leases	3.28%	2.97%
Finance leases	5.38%	5.40%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Operating leases
2024	$ 18
2025	16
2026	13
2027	12
2028	10
2029 and thereafter	51
Total lease payments	120
Less: imputed interest	21
Total	$ 99
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Accounts payable and accrued liabilities
Finance leases
2024	$ 5
2025	4
2026	4
2027	3
2028	3
2029 and thereafter	15
Total lease payments	34
Less: imputed interest	6
Total	$ 28	$ 29

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Loss Contingencies [Line Items]
Raw material purchased	$ 370,000,000	$ 512,000,000	$ 405,000,000
Long term purchase commitment related to information technology	$ 19,000,000
Purchase agreement period	5 years
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]	Accounts payable and accrued liabilities	Accounts payable and accrued liabilities
Charges for environmental expense	$ 1,000,000	$ 1,000,000	$ 1,000,000
Environmental Remediation Expense, Statement of Income or Comprehensive Income [Extensible Enumeration]	Cost of sales	Cost of sales	Cost of sales
Cash payments for environmental reserves	$ 1,000,000	$ 2,000,000	$ 2,000,000
Settlement amount	9,000,000	11,000,000	37,000,000
(Provision) benefit for income taxes	28,000,000	(102,000,000)	(123,000,000)
Respirator Liabilities [Member]
Loss Contingencies [Line Items]
Respirator reserve	$ 38,000,000	39,000,000
Respirator reserve period	10 years
Respirator Liabilities [Member] | Selling and Administrative Expenses [Member]
Loss Contingencies [Line Items]
Respirator charge	$ 8,000,000	6,000,000	25,000,000
Brazil Indirect Tax Settlements
Loss Contingencies [Line Items]
(Provision) benefit for income taxes			12,000,000
Brazil Indirect Tax Settlements | Net Sales And Other Operating Revenues
Loss Contingencies [Line Items]
Income tax credit recovery			9,000,000
Brazil Indirect Tax Settlements | Other Nonoperating Income (Expense) [Member]
Loss Contingencies [Line Items]
Estimated charge for damages			3,000,000
Environmental Matters [Member]
Loss Contingencies [Line Items]
Reserved for environmental matters	5,000,000	4,000,000
Environmental Matters [Member] | Operating and Maintenance Component [Member]
Loss Contingencies [Line Items]
Reserved for environmental matters	3,000,000	3,000,000
Per Accident for Auto [Member]
Loss Contingencies [Line Items]
Self-insured liability	500,000
Per Occurrence for All Other [Member]
Loss Contingencies [Line Items]
Self-insured liability	2,000,000
Per Accident for U.S. Workers' Compensation [Member]
Loss Contingencies [Line Items]
Self-insured liability	1,000,000
Maximum [Member]
Loss Contingencies [Line Items]
Retention for medical costs per person per annum	275,000
Non-Controlling Interests [Member]
Loss Contingencies [Line Items]
Raw material purchased	192,000,000	235,000,000	$ 135,000,000
Accounts payable and accrued liabilities	$ 11,000,000	$ 31,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Components of Purchase Commitments (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Long-term Purchase Commitment [Line Items]
Payments Due by Fiscal Year 2024	$ 249
Payments Due by Fiscal Year 2025	223
Payments Due by Fiscal Year 2026	217
Payments Due by Fiscal Year 2027	197
Payments Due by Fiscal Year 2028	122
Payments Due Thereafter	1,477
Payments Due, Total	2,485
Reinforcement Materials [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Fiscal Year 2024	208
Payments Due by Fiscal Year 2025	185
Payments Due by Fiscal Year 2026	181
Payments Due by Fiscal Year 2027	161
Payments Due by Fiscal Year 2028	101
Payments Due Thereafter	1,266
Payments Due, Total	2,102
Performance Chemicals [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Fiscal Year 2024	41
Payments Due by Fiscal Year 2025	38
Payments Due by Fiscal Year 2026	36
Payments Due by Fiscal Year 2027	36
Payments Due by Fiscal Year 2028	21
Payments Due Thereafter	211
Payments Due, Total	$ 383

Financial Information by Segm_3

Financial Information by Segment & Geographic Area - Additional Information (Detail)	12 Months Ended
	Sep. 30, 2023 Segment
Segment Reporting Information [Line Items]
Number of business reportable segments	2

Financial Information by Segm_4

Financial Information by Segment & Geographic Area - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 3,931	$ 4,321	$ 3,409
Depreciation and amortization	144	146	160
Income (Loss) from Equity Method Investments	5	10	3
Income (loss) from operations before income taxes	451	335	406
Assets	3,604	3,525	3,306
Total expenditures for additions to long-lived assets	265	221	198
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	3,788	4,158	3,251
Depreciation and amortization	142	145	159
Income (Loss) from Equity Method Investments	5	10	4
Income (loss) from operations before income taxes	607	642	550
Assets	3,105	3,149	3,029
Total expenditures for additions to long-lived assets	257	217	193
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues	143	163	158
Depreciation and amortization	2	1	1
Income (Loss) from Equity Method Investments			(1)
Income (loss) from operations before income taxes	(156)	(307)	(144)
Assets	499	376	277
Total expenditures for additions to long-lived assets	8	4	5
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues		98	57
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	2,563	2,673	1,838
Depreciation and amortization	70	70	70
Income (Loss) from Equity Method Investments	2	4
Income (loss) from operations before income taxes	482	408	329
Assets	1,632	1,691	1,421
Total expenditures for additions to long-lived assets	149	114	104
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenues		16	8
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	1,225	1,388	1,156
Depreciation and amortization	72	72	73
Income (Loss) from Equity Method Investments	3	5	2
Income (loss) from operations before income taxes	125	234	211
Assets	1,473	1,458	1,325
Total expenditures for additions to long-lived assets	$ 108	100	80
Purification Solutions [Member]
Segment Reporting Information [Line Items]
Revenues		97	257
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		97	257
Depreciation and amortization		3	16
Income (Loss) from Equity Method Investments		1	2
Income (loss) from operations before income taxes			10
Assets			283
Total expenditures for additions to long-lived assets		$ 3	$ 9

Financial Information by Segm_5

Financial Information by Segment & Geographic Area - Financial Information by Reportable Segment (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 3,931	$ 4,321	$ 3,409
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenues		98	57
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenues		$ 16	$ 8

Financial Information by Segm_6

Financial Information by Segment & Geographic Area - Sales of Equity Method Affiliate, Discounting Charges for Certain Notes Receivable, by- productive Revenue, Indirect Tax Settlement Credits, and Insurance Recoveries (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 3,931	$ 4,321	$ 3,409
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues	143	163	158
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues	132	162	153
Unallocated and Other [Member] | By-product Sales [Member]
Segment Reporting Information [Line Items]
Revenues	5	8	8
Unallocated and Other [Member] | Other [Member]
Segment Reporting Information [Line Items]
Revenues	$ 6	$ (7)	$ (3)

Financial Information by Segm_7

Financial Information by Segment & Geographic Area - 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	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Interest expense	$ (90)	$ (56)	$ (49)
Gain on sale of land	1	17
Loss on sale of business and asset impairment charge	3	207
Gain on bargain purchase of a business		24
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(90)	(56)	(49)
Unallocated corporate costs	(54)	(59)	(58)
General unallocated income (expense)	22	1
Less: Equity in earnings of affiliated companies, net of tax	5	10	3
Income from continuing operations before income taxes and equity in earnings of affiliated companies	(156)	(307)	(144)
Certain Items [Member]
Segment Reporting Information [Line Items]
Gain on sale of land	1	17
Legal and environmental matters and reserves	(10)	(9)	(25)
Acquisition and integration-related charges	(4)	(6)	(5)
Global restructuring activities	(4)	(3)	(11)
Loss on sale of business and asset impairment charge	(3)	(207)
Other certain items	(2)		(1)
Gain on bargain purchase of a business		24
Employee benefit plan settlement and other charges		1	(4)
Indirect tax settlement credits			12
Total certain items, pre-tax	(29)	(183)	$ (34)
Certain Items [Member] | Argentina [Member]
Segment Reporting Information [Line Items]
Controlled currency devaluation loss	$ (7)
Certain Items [Member] | Specialty Fluids [Member]
Segment Reporting Information [Line Items]
Divestiture related benefit		5
Certain Items [Member] | Purification Solutions [Member]
Segment Reporting Information [Line Items]
Divestiture related charges		$ (5)

Financial Information by Segm_8

Financial Information by Segment & Geographic Area - Revenue from External Customers and Property, Plant and Equipment Information by Geographic Area (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	$ 3,931	$ 4,321	$ 3,409
Net property, plant and equipment	1,412	1,270
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	738	842	668
Net property, plant and equipment	588	524
China [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	972	1,129	858
Net property, plant and equipment	356	333
Other Countries [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	2,221	2,350	$ 1,883
Net property, plant and equipment	$ 468	$ 413

Financial Information by Segm_9

Financial Information by Segment & Geographic Area - Revenue from External Customers by Geographic Region (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 3,931	$ 4,321	$ 3,409
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	3,788	4,158	3,251
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	143	163	158
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		98	57
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	2,563	2,673	1,838
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		16	8
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	1,225	1,388	1,156
Purification Solutions [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		97	257
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		97	257
Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	1,425	1,534	1,129
Americas [Member] | Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	1,046	1,072	708
Americas [Member] | Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	379	419	311
Americas [Member] | Purification Solutions [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		43	110
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	1,486	1,630	1,300
Asia Pacific [Member] | Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	995	1,049	777
Asia Pacific [Member] | Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	491	567	489
Asia Pacific [Member] | Purification Solutions [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		14	34
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	877	994	822
Europe, Middle East and Africa [Member] | Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	522	552	353
Europe, Middle East and Africa [Member] | Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 355	402	356
Europe, Middle East and Africa [Member] | Purification Solutions [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		$ 40	$ 113