Cabot (CBT) 10-Q 6 Feb 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2019	Feb. 04, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	CBT
Entity Registrant Name	Cabot Corporation
Entity Central Index Key	0000016040
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		56,679,597
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	1-5667
Entity Tax Identification Number	04-2271897
Entity Address, Address Line One	Two Seaport Lane
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02210-2019
City Area Code	617
Local Phone Number	345-0100
Security Exchange Name	NYSE
Title of 12(b) Security	Common Stock, $1 par value per share
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales and other operating revenues	$ 727	$ 821
Cost of sales	586	655
Gross profit	141	166
Selling and administrative expenses	64	73
Research and technical expenses	14	16
Income (loss) from operations	63	77
Interest and dividend income	3	2
Interest expense	(14)	(15)
Other income (expense)	(2)	6
Income (loss) from continuing operations before income taxes and equity in earnings of affiliated companies	50	70
(Provision) benefit for income taxes	(4)	7
Net income (loss)	46	77
Net income (loss) attributable to noncontrolling interests, net of tax	5	8
Net income (loss) attributable to Cabot Corporation	$ 41	$ 69
Weighted-average common shares outstanding:
Basic	56.9	59.9
Diluted	57	60.1
Earnings per common share:
Basic	$ 0.71	$ 1.14
Diluted	$ 0.70	$ 1.14

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 46	$ 77
Other comprehensive income (loss), net of tax
Foreign currency translation adjustment, net of tax (provision) benefit of $(1) and $2	43	(24)
Derivatives: net investment hedges
(Gains) losses reclassified to interest expense, net of tax provision (benefit) of $— and $—	(1)	(1)
Pension and other postretirement benefit liability adjustments
Pension and other postretirement benefit liability adjustments arising during the period, net of tax	1	22
Other comprehensive income (loss)	43	(3)
Comprehensive income (loss)	89	74
Net income (loss) attributable to noncontrolling interests, net of tax	5	8
Foreign currency translation adjustment attributable to noncontrolling interests, net of tax	3
Comprehensive income (loss) attributable to noncontrolling interests, net of tax	8	8
Comprehensive income (loss) attributable to Cabot Corporation	$ 81	$ 66

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency translation adjustment, tax provision (benefit)	$ (1)	$ 2

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Current assets:
Cash and cash equivalents	$ 173	$ 169
Accounts and notes receivable, net of reserve for doubtful accounts of $3 and $3	485	530
Inventories:
Raw materials	110	107
Finished goods	313	305
Other	56	54
Total inventories	479	466
Prepaid expenses and other current assets	59	45
Total current assets	1,196	1,210
Property, plant and equipment, net	1,395	1,348
Goodwill	92	90
Equity affiliates	39	39
Intangible assets, net	97	96
Deferred income taxes	161	163
Other assets	171	58
Total assets	3,151	3,004
Current liabilities:
Short-term borrowings	4	33
Accounts payable and accrued liabilities	544	537
Income taxes payable	19	22
Current portion of long-term debt	7	7
Total current liabilities	574	599
Long-term debt	1,095	1,024
Deferred income taxes	41	41
Other liabilities	289	206
Commitments and contingencies (Note G)
Preferred stock:
Authorized: 2,000,000 shares of $1 par value Issued and Outstanding: None and none
Common stock:
Authorized: 200,000,000 shares of $1 par value issued: and shares Outstanding: and shares	57	57
Less cost of 169,865 and 169,865 shares of common treasury stock	(5)	(5)
Retained earnings	1,329	1,337
Accumulated other comprehensive income (loss)	(354)	(391)
Total Cabot Corporation stockholders' equity	1,027	998
Noncontrolling interests	125	136
Total stockholders' equity	1,152	1,134
Total liabilities and stockholders' equity	$ 3,151	$ 3,004

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 3	$ 3
Preferred stock, authorized shares	2,000,000	2,000,000
Preferred stock, par value	$ 1	$ 1
Preferred stock, Issued shares	0	0
Preferred stock, Outstanding shares	0	0
Common stock, authorized shares	200,000,000	200,000,000
Common stock, par value	$ 1	$ 1
Common stock, issued shares	56,825,282	57,250,454
Common stock, outstanding shares	56,655,417	57,080,589
Common treasury stock, shares	169,865	169,865

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities:
Net income (loss)	$ 46	$ 77
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation and amortization	39	35
Deferred tax provision (benefit)	(6)	(23)
Employee benefit plan settlement		6
Non-cash compensation	1	5
Changes in assets and liabilities:
Accounts and notes receivable	54	47
Inventories	(7)	(83)
Prepaid expenses and other current assets	(21)	(2)
Accounts payable and accrued liabilities	3	(75)
Income taxes payable	(3)	(15)
Other liabilities	(2)	(12)
Cash dividends received from equity affiliates	1	1
Cash provided (used) by operating activities	105	(39)
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(68)	(54)
Cash paid for acquisition of business	(8)
Other	(1)
Cash provided (used) by investing activities	(77)	(54)
Cash Flows from Financing Activities:
Borrowings under financing arrangements		18
Proceeds from (repayments of) issuance of commercial paper, net	(29)	248
Proceeds from long-term debt	97
Repayments of long-term debt	(48)	(74)
Repayments of redeemable preferred stock		(25)
Purchases of common stock	(34)	(62)
Proceeds from sales of common stock	1
Cash dividends paid to noncontrolling interests	(11)	(11)
Cash dividends paid to common stockholders	(20)	(20)
Cash provided (used) by financing activities	(44)	74
Effects of exchange rate changes on cash	20	(14)
Increase (decrease) in cash and cash equivalents	4	(33)
Cash and cash equivalents at beginning of period	169	175
Cash and cash equivalents at end of period	$ 173	$ 142

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions	Total	Common Stock, Net of Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Cabot Corporation Stockholders' Equity [Member]	Noncontrolling Interests [Member]
Beginning Balance at Sep. 30, 2018	$ 1,279	$ 54		$ 1,417	$ (317)	$ 1,154	$ 125
Beginning Balance, Shares at Sep. 30, 2018		60,367
Net income (loss)	77			69		69	8
Total other comprehensive income (loss)	(3)				(3)	(3)
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Issuance of stock under equity compensation plans, Shares		344
Amortization of share-based compensation	5		$ 5			5
Purchase and retirement of common stock	(62)	$ (1)	(5)	(56)		(62)
Purchase and retirement of common stock, Shares		(1,201)
Ending Balance at Dec. 31, 2018	1,276	$ 53		1,410	(320)	1,143	133
Ending Balance, Shares at Dec. 31, 2018		59,510
Beginning Balance at Sep. 30, 2019	1,134	$ 52		1,337	(391)	998	136
Beginning Balance, Shares at Sep. 30, 2019		57,081
Adoption of accounting standards				3	(3)
Net income (loss)	46			41		41	5
Total other comprehensive income (loss)	43				40	40	3
Cash dividends paid, Common stock, per share	(20)			(20)		(20)
Cash dividends declared to noncontrolling interests	(19)						(19)
Issuance of stock under equity compensation plans	1		1			1
Issuance of stock under equity compensation plans, Shares		273
Amortization of share-based compensation	1		1			1
Purchase and retirement of common stock	(34)		$ (2)	(32)		(34)
Purchase and retirement of common stock, Shares		(699)
Ending Balance at Dec. 31, 2019	$ 1,152	$ 52		$ 1,329	$ (354)	$ 1,027	$ 125
Ending Balance, Shares at Dec. 31, 2019		56,655

Consolidated Statements of Ch_2

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

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	A. Basis of Presentation The consolidated financial statements have been prepared in conformity with accounting policies generally accepted in the United States (“U.S.”) and include the accounts of Cabot Corporation (“Cabot” or the “Company”) and its wholly owned subsidiaries and majority-owned and controlled U.S. and non-U.S. subsidiaries. Additionally, Cabot considers consolidation of entities over which control is achieved through means other than voting rights. Intercompany transactions have been eliminated in consolidation. The unaudited consolidated financial statements have been prepared in accordance with the requirements of Form 10-Q and consequently do not include all disclosures required by Form 10-K. Additional information may be obtained by referring to Cabot’s Annual Report on Form 10-K for its fiscal year ended September 30, 2019 (“2019 10-K”). The financial information submitted herewith is unaudited and reflects all adjustments which are, in the opinion of management, necessary to provide a fair statement of the results for the interim periods ended December 31, 2019 and 2018. All such adjustments are of a normal recurring nature. The results for interim periods are not necessarily indicative of the results to be expected for the fiscal year. In June 2019, the Company completed the sale of its Specialty Fluids business. The transaction did not meet the criteria to be reported as a discontinued operation. Therefore, prior periods’ consolidated financial statements and disclosures have not been recast. Effective October 1, 2019, the Company adopted the accounting standard for leases issued by the Financial Accounting Standards Board (“FASB”) in February 2016 . The Company used a modified retrospective optional transition method, which is discussed in detail in Note B.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	B. Significant Accounting Policies Revenue Recognition Cabot recognizes revenue when its customers obtain control of promised goods or services. The revenue recognized is the amount of consideration that the Company expects to receive in exchange for those goods or services. The Company’s contracts with customers are generally for products only and do not include other performance obligations. Generally, Cabot considers purchase orders, which in some cases are governed by master supply agreements, to be contracts with customers. The transaction price as specified on the purchase order or sales contract is considered the standalone selling price for each distinct product. To determine the transaction price at the time when revenue is recognized, the Company evaluates whether the price is subject to adjustments, such as for returns, discounts or volume rebates, which are stated in the customer contract, to determine the net consideration to which the Company expects to be entitled. Revenue from product sales is recognized based on a point in time model when control of the product is transferred to the customer, which typically occurs upon shipment or delivery of the product to the customer and title, risk and rewards of ownership have passed to the customer. The Company has an immaterial amount of revenue that is recognized over time. Payment terms typically range from zero to ninety days. Shipping and handling costs incurred after the transfer of control of a product to the customer are billed to the customer and are recorded as sales revenue, as the Company considers these to be fulfillment costs. Shipping and handling costs are expensed in the period incurred and included in Cost of sales within the Consolidated Statement of Operations. Taxes collected on sales to customers are excluded from the transaction price. The Company generally provides a warranty that its products will substantially conform to the identified specifications. The Company’s liability typically is limited to either a credit equal to the purchase price or replacement of the non-conforming product. Returns under warranty have historically been immaterial. The Company does not have contract assets or liabilities that are material. As permitted by the FASB’s revenue recognition standard, Revenue from Contracts with Customers , when the period of time between the transfer of control of the goods and the time the customer pays for the goods is one year or less, the Company does not consider there to be a significant financing component associated with the contract. Intangible Assets and Goodwill Impairment The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for assets acquired and liabilities assumed in an acquisition are allocated to the assets and liabilities based on their fair values at the date of acquisition. The Company uses assumptions and estimates in determining the fair value of assets acquired and liabilities assumed in a business combination. The determination of the fair value of intangible assets requires the use of significant judgment with regard to assumptions used in the valuation model. The Company estimates the fair value of identifiable acquisition-related intangible assets principally based on projections of cash flows that will arise from these assets. The projected cash flows are discounted to determine the fair value of the assets at the dates of acquisition. Definite-lived intangible assets, which are comprised of trademarks, customer relationships and developed technologies, are amortized over their estimated useful lives and are reviewed for impairment when indication of potential impairment exists, such as a significant reduction in cash flows associated with the assets. Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value assigned to the net tangible and identifiable intangible assets acquired. Goodwill is not amortized, but is reviewed for impairment annually as of August 31, or when events or changes in the business environment indicate that the carrying value of the reporting unit may exceed its fair value. A reporting unit, for the purpose of the impairment test, is at or below the operating segment level, and constitutes a business for which discrete financial information is available and regularly reviewed by segment management. Reinforcement Materials, and the fumed metal oxides and specialty compounds product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of December 31, 2019. For the purpose of the goodwill impairment test, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value, an additional quantitative evaluation is performed. Alternatively, the Company may elect to proceed directly to the quantitative goodwill impairment test. If based on the quantitative evaluation the fair value of the reporting unit is less than its carrying amount, a goodwill impairment loss would result. The goodwill impairment loss would be the amount by which the carrying value of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. The fair value of a reporting unit is based on discounted estimated future cash flows. The fair value is also benchmarked against a market approach using the guideline public company method. The assumptions used to estimate fair value include management’s best estimates of future growth rates, operating cash flows, capital expenditures and discount rates over an estimate of the remaining operating period at the reporting unit level. Based on the Company’s most recent annual goodwill impairment test performed as of August 31, 2019, the fair values of the Reinforcement Materials, Fumed Metal Oxides and Specialty Compounds reporting units were substantially in excess of their carrying values. Long-lived Assets Impairment The Company’s long-lived assets primarily include property, plant and equipment, intangible assets and long-term investments. The carrying values of long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. To test for impairment of assets, the Company generally uses a probability-weighted estimate of the future undiscounted net cash flows of the assets over their remaining lives to determine if the value of the asset is recoverable. Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable. An asset impairment is recognized when the carrying value of the asset is not recoverable based on the analysis described above, in which case the asset is written down to its fair value. If the asset does not have a readily determinable fair value, a discounted cash flow model may be used to determine the fair value of the asset. In circumstances when an asset does not have separately identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset. The Company continues to consider strategic options for its Purification Solutions business. Depending on the actions taken, there could be a negative impact on the fair value of the Purification Solutions reporting unit, which may lead to an impairment. Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The depreciable lives for buildings, machinery and equipment, and other fixed assets are between twenty and twenty-five years, ten and twenty-five years, and three and twenty-five years, respectively. The cost and accumulated depreciation for property, plant and equipment sold, retired, or otherwise disposed of are removed from the Consolidated Balance Sheets and resulting gains or losses are included in earnings in the Consolidated Statements of Operations. Expenditures for repairs and maintenance are charged to expenses as incurred. Expenditures for major renewals and betterments, which significantly extend the useful lives of existing plant and equipment, are capitalized and depreciated. Income Tax in Interim Periods The Company records its tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period. Valuation allowances are provided against the future tax benefits that arise from the deferred tax assets in jurisdictions for which no benefit can be recognized. The estimated annual effective tax rate may be significantly impacted by nondeductible expenses and the Company’s projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised. Inventory Valuation Inventories are stated at the lower of cost or net realizable value. The cost of inventory is determined using the FIFO method. Cabot periodically reviews inventory for both potential obsolescence and potential declines in anticipated selling prices. In this review, the Company makes assumptions about the future demand for and market value of the inventory, and based on these assumptions estimates the amount of any obsolete, unmarketable, slow moving, or overvalued inventory. Cabot writes down the value of these inventories by an amount equal to the difference between the cost of the inventory and its estimated net realizable value. Pensions and Other Postretirement Benefits The Company recognizes the funded status of defined benefit pension and other postretirement benefit plans as an asset or liability. This amount is defined as the difference between the fair value of plan assets and the benefit obligation. Pension and post-retirement benefit costs other than service cost are included in Other income (expense) in the Consolidated Statement of Operations. The Company is required to recognize as a component of Other comprehensive income (loss), net of tax, the actuarial gains/losses and prior service costs/credits that arise but were not previously required to be recognized as components of net periodic benefit cost. Other comprehensive income (loss) is adjusted as these amounts are later recognized in income as components of net periodic benefit cost. Accumulated Other Comprehensive Income (Loss) Accumulated other comprehensive income (loss) (“AOCI”), which is included as a component of stockholders’ equity, includes unrealized gains or losses on derivative instruments, currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments. Recently Adopted Accounting Standards In February 2016, the FASB issued a new standard for the accounting for leases. This standard requires lessees to recognize assets and liabilities for most leases, but recognize expenses on their income statements in a manner that is similar to the historical accounting treatment for leases. The Company adopted the standard on October 1, 2019 using the modified retrospective optional transition method. Accordingly, leases in the prior period continue to be reported and disclosed in accordance with the Company’s historical accounting treatment. The Company elected the package of practical expedients that permits the Company to not reassess the identification, classification and initial direct costs of leases commencing before the October 1, 2019 effective date and to exclude short-term leases from the balance sheet. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases or the practical expedient to not separate lease and non-lease components to existing leases, as well as new leases, through transition. The Company allocates the total consideration to the lease components and non-lease components on an observable stand-alone price basis to all asset classes. Adoption of the new lease standard resulted in the recognition of operating lease right-of-use (“ROU”) assets and operating lease liabilities of approximately $106 million and $111 million, respectively, as of October 1, 2019. Refer to Note H for further details regarding the balance sheet classification of these items. The difference between the operating lease ROU assets and operating lease liabilities reflects the reclassification of historical deferred rent balances of approximately $ 5 million. The effects of transition to the new standard resulted in no cumulative adjustment to retained earnings in the period of adoption. The standard did not materially impact the Company’s Consolidated Statement of Operations or Consolidated Statement of Cash Flows. The new standard did not have a material impact on the Company’s liquidity or debt-covenant compliance under its current debt agreements. In February 2018, the FASB issued a new standard that allows entities to reclassify from AOCI to Retained earnings stranded tax effects resulting from changes made as a result of the Tax Cuts and Jobs Act of 2017 (the “Act”). The Company adopted this standard on October 1, 2019 which resulted in the reclassification of a $2 million net gain from AOCI to Retained earnings. The reclassification was primarily related to the Company’s pension plans and derivative instruments. Recent Accounting Pronouncements In June 2016, the FASB issued a new standard on measurement of credit losses. The standard introduces an "expected loss" impairment model that applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables and other financial assets. Entities are required to estimate expected credit losses over the life of financial assets and record an allowance against the assets’ amortized cost basis to present them at the amount expected to be collected. The new standard is effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The Company is evaluating this standard and the timing of its adoption. The Company does not expect the adoption of this standard to materially impact the Company’s consolidated financial statements.

Acquisitions

Acquisitions	3 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Acquisitions	C. Acquisitions NSCC Carbon (Jiangsu) Co. Ltd In September 2018 Shenzhen Sanshun Nano New Materials Co., Ltd In December 2019, the Company entered into an agreement to purchase Shenzhen Sanshun Nano New Materials Co., Ltd (SUSN), a leading carbon nanotube producer, for approximately $115 million through cash considerations of $100 million and debt assumed of $15 million. The transaction is expected to close in the second quarter of fiscal 2020 and will be accounted for as a business combination. Upon closing, the operating results of the business will be included in the Company’s Performance Chemicals segment.

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	D. Employee Benefit Plans Net periodic defined benefit pension and other postretirement benefit costs include the following: Three Months Ended December 31 2019 2018 2019 2018 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Service cost $ — $ 1 $ — $ 2 $ — $ — $ — $ — Interest cost 1 1 1 2 — — — — Expected return on plan assets (1 ) (2 ) (2 ) (4 ) — — — — Amortization of prior service credit — — — — — — — — Amortization of actuarial loss — 1 — 1 — — — — Settlement and curtailment gain — — — (6 ) — — — — Net periodic benefit (credit) cost $ — $ 1 $ (1 ) $ (5 ) $ — $ — $ — $ — U.S. Cash Balance Plan Termination In fiscal 2019, the Company’s Board of Directors approved a resolution to terminate the Company’s U.S. pension plan. The Company commenced the U.S. plan termination process during the third quarter of fiscal 2019 and expects to complete the transfer of the U.S. plan’s assets to participants in fiscal year 2020 , pending an Internal Revenue Service (“IRS”) determination letter. The pension liability will be settled through a combination of lump-sum payment s and purchased annuit ies . Upon settlement of the benefit liabilities accrued in the plan, the Company will recognize a loss associated with the release of approximately $ 13 million from AOCI in the Consolidated Balance Sheet to Other income (expense) in the Consolidated Statement of Operations. Curtailments and Settlements of Employee Benefit Plans In fiscal 2019, the Company transferred the majority of the defined benefit obligations and pension plan assets in one of its foreign defined benefit plans to a multi-employer plan. This action moved the administrative, asset custodial, asset investment, actuarial, communication and benefit payment obligations to the multi-employer fund administrator. As a result of the transfer, a pre-tax gain of $6 million was recorded in the first quarter of fiscal 2019, which is included in Other income (expense) in the Consolidated Statement of Operations. In addition, as part of the transfer, the Company recorded a $3 million charge in the first quarter of fiscal 2019 reflecting the Company’s agreement to fund the actuarial loss gap between the terminated plan and the multi-employer plan. This charge is included in Other income (expense) in the Consolidated Statement of Operations.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	E. Goodwill and Intangible Assets The carrying amount of goodwill attributable to each reportable segment with goodwill balances and the changes in those balances during the three month period ended December 31, 2019 are as follows: Reinforcement Materials Performance Chemicals Total (In millions) Balance at September 30, 2019 $ 50 $ 40 $ 90 Foreign currency impact 1 1 2 Balance at December 31, 2019 $ 51 $ 41 $ 92 The following table provides information regarding the Company’s intangible assets: December 31, 2019 September 30, 2019 Gross Carrying Value Accumulated Amortization Net Intangible Assets Gross Carrying Value Accumulated Amortization Net Intangible Assets (In millions) Intangible assets with finite lives Developed technologies $ 51 $ (5 ) $ 46 $ 50 $ (5 ) $ 45 Trademarks 8 — 8 8 — 8 Customer relationships 58 (15 ) 43 57 (14 ) 43 Total intangible assets $ 117 $ (20 ) $ 97 $ 115 $ (19 ) $ 96 Intangible assets are amortized over their estimated useful lives, which range between twelve and twenty-five years, with a weighted average amortization period of approximately nineteen years. Amortization expense for both of the three month periods ended December 31, 2019 and 2018 was $1 million and is included in Cost of sales, Selling and administrative expenses, and Research and technical expenses in the Consolidated Statements of Operations.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Dec. 31, 2019
Stockholders Equity Note [Abstract]
Accumulated Other Comprehensive Income (Loss)	F. Accumulated Other Comprehensive Income (Loss) Comprehensive income combines net income (loss) and other comprehensive income items, which are reported as components of stockholders’ equity in the accompanying Consolidated Balance Sheets. Changes in each component of AOCI, net of tax, were as follows: Currency Translation Adjustment Unrealized Gains on Investments Pension and Other Postretirement Benefit Liability Adjustments Total (In millions) Balance at September 30, 2019, attributable to Cabot Corporation $ (338 ) $ 1 $ (54 ) $ (391 ) Other comprehensive income (loss) before reclassifications 43 — — 43 Amounts reclassified from AOCI (1 ) — 1 — Adoption of accounting standards (3 ) (1 ) 1 (3 ) Less: Other comprehensive income (loss) attributable to noncontrolling interests 3 — — 3 Balance at December 31, 2019, attributable to Cabot Corporation $ (302 ) $ — $ (52 ) $ (354 ) The amounts reclassified out of AOCI and into the Consolidated Statements of Operations in the three months ended December 31, 2019 and 2018 were as follows: Affected Line Item in the Consolidated Three Months Ended December 31 Statements of Operations 2019 2018 (In millions) Derivatives: net investment hedges (Gains) losses reclassified to interest expense Interest expense $ (1 ) $ (1 ) Pension and other postretirement benefit liability adjustment Amortization of actuarial losses Net Periodic Benefit Cost - see Note D for details 1 1 Settlement and curtailment gain Net Periodic Benefit Cost - see Note D for details — (6 ) Total before tax — (6 ) Tax impact Provision (benefit) for income taxes — (3 ) Total after tax $ — $ (9 )

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	G. Commitments and Contingencies Purchase 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. For these purchase commitments, the amounts included in the table below are based on market prices at December 31, 2019, which may differ from actual market prices at the time of purchase. Payments Due by Fiscal Year Remainder of Fiscal 2020 2021 2022 2023 2024 Thereafter Total (In millions) Reinforcement Materials $ 174 $ 132 $ 117 $ 107 $ 106 $ 1,211 $ 1,847 Performance Chemicals 50 57 55 36 31 405 634 Purification Solutions 3 1 — — — — 4 Total $ 227 $ 190 $ 172 $ 143 $ 137 $ 1,616 $ 2,485 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. 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 December 31, 2019 and September 30, 2019, Cabot had $12 million and $13 million, respectively, reserved for environmental matters. 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. Cash payments related to these environmental matters were $2 million and $1 million in the first three months of fiscal 2020 and fiscal 2019, respectively. 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. Respirator Liabilities Cabot has exposure in connection with a safety respiratory products business that a subsidiary acquired from American Optical Corporation (“AO”) in an April 1990 asset purchase transaction. The subsidiary manufactured respirators under the AO brand and disposed of that business in July 1995. In connection with its acquisition of the business, the subsidiary agreed, in certain circumstances, to assume a portion of AO’s liabilities, including costs of legal fees together with amounts paid in settlements and judgments, allocable to AO respiratory products used prior to the 1990 purchase by the Cabot subsidiary. In exchange for the subsidiary’s assumption of certain of AO’s respirator liabilities, AO agreed to provide to the subsidiary the benefits of: (i) AO’s insurance coverage for the period prior to the 1990 acquisition and (ii) a former owner’s indemnity of AO holding it harmless from any liability allocable to AO respiratory products used prior to May 1982. As more fully described in the 2019 10-K, the respirator liabilities generally involve claims for personal injury, including asbestosis, silicosis and coal worker’s pneumoconiosis, allegedly resulting from the use of respirators that are alleged to have been negligently designed and/or labeled. Neither Cabot, nor its past or present subsidiaries, at any time manufactured asbestos or asbestos-containing products. At no time did this respiratory product line represent a significant portion of the respirator market. Cabot has a reserve to cover its expected share of liability for existing and future respirator liability claims, which at December 31, 2019 and September 30, 2019, was $34 million and $35 million, respectively. The Company made payments related to its respirator liability of $1 million in the first three months of both fiscal 2020 and fiscal 2019. The Company’s current estimate of the cost of its share of existing and future respirator liability claims is based on facts and circumstances existing at this time. Developments that could affect the Company’s estimate include, but are not limited to, (i) significant changes in the number of future claims, (ii) changes in the rate of dismissals without payment of pending claims, (iii) significant changes in the average cost of resolving claims, including potential settlements of groups of claims, (iv) significant changes in the legal costs of defending these claims, (v) changes in the nature of claims received, (vi) trial and appellate outcomes, (vi i ) changes in the law and procedure applicable to these claims, (vii i ) the financial viability of the parties that contribute to the settlement of respirator claims, ( ix ) a change in the availability of insurance coverage maintained by ce rtain of the parties that contribute to the settlement of respirator claims, or the indemnity provided by a former owner of the business, (x) changes in the allocation of costs among the various parties paying legal and settlement costs, and (x i ) 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. Accordingly, the actual amount of these liabilities for existing and future claims could be larger than the reserved amount. Other Matters The Company has various other lawsuits, claims and contingent liabilities arising in the ordinary course of its business and with respect to its divested businesses. The Company does not believe that any of these matters will have a material adverse effect on its financial position; however, litigation is inherently unpredictable. Cabot could incur judgments, enter into settlements or revise its expectations regarding the outcome of certain matters, and such developments could have a material impact on its results of operations in the period in which the amounts are accrued or its cash flows in the period in which the amounts are paid.

Leases

Leases	3 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	H. Leases The Company determines if an arrangement is a lease at inception. The Company considers a contract to be or to contain a lease if the contract conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration. A lease liability is recorded at commencement for the net present value of future lease payments over the lease term. The discount rate used is generally the Company’s estimated incremental borrowing rate based on credit-adjusted and term-specific discount rates, using a third-party yield curve. A ROU asset is recorded and recognized at commencement at the lease liability amount, including initial direct costs incurred, and is reduced for lease incentives received. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. In the normal course of its business, the Company enters into various leases as the lessee, primarily related to certain transportation vehicles, warehouse facilities, office space, and machinery and equipment. These leases have remaining lease terms between 1 and 15 years, some of which may include options to extend the leases for up to 15 years or options to terminate the leases. The Company’s land leases have remaining lease terms up to 70 years. Some lease arrangements require variable payments that are dependent on usage, output, or index-based adjustments. The Company does not have material variable lease payments. The Company has elected not to recognize short-term leases on the balance sheet for all underlying asset classes. Short-term leases are leases that, at the commencement date, have a lease term of twelve months or less and do not include a purchase option that the Company is reasonably certain to exercise. Short-term leases are expensed on a straight-line basis over the lease term. The components of the Company’s lease costs were as follows: Three Months Ended December 31 2019 (In millions) Operating lease cost $ 6 Finance lease cost 1 Total lease cost $ 7 Short-term and variable lease costs were less than $1 Supplemental cash flow information related to the Company’s leases was as follows: Three Months Ended December 31 2019 (In millions) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6 Right-of-use assets obtained in exchange for new operating lease liabilities $ 2 Right-of-use assets obtained in exchange for new finance lease liabilities $ 20 Supplemental balance sheet information related to the Company’s leases was as follows: Description Balance Sheet Classification December 31, 2019 (In millions) Lease ROU assets: Operating Other assets $ 102 Finance Net property, plant and equipment 46 Total lease ROU assets $ 148 Lease liabilities: Current: Operating Accounts payable and accrued liabilities $ 20 Finance Current portion of long-term debt 3 Long-term: Operating Other liabilities 88 Finance Long-term debt 29 Total lease liabilities $ 140 The following table presents the weighted-average remaining lease term and discount rates for the Company’s leases as of December 31, 2019: Description December 31, 2019 Weighted-average remaining lease term (years): Operating leases 16 Finance leases 13 Weighted-average discount rate: Operating leases 2.29 % Finance leases 4.55 % Future minimum lease payments under non-cancelable operating and finance leases as of December 31, 2019 are as follows: Years Ended September 30 Operating leases Finance leases (In millions) Remainder of fiscal 2020 $ 17 $ 4 2021 14 4 2022 10 4 2023 9 4 2024 9 4 2025 and thereafter 69 25 Total lease payments 128 45 Less: imputed interest 20 13 Total $ 108 $ 32 The Company’s future minimum lease payments under noncancelable leases as of September 30, 2019 were as follows: Years Ended September 30 Operating leases Capital leases (In millions) 2020 $ 23 $ 3 2021 14 3 2022 9 3 2023 9 3 2024 8 2 2025 and thereafter 68 7 Total lease payments 131 21 Less: imputed interest — 9 Total $ 131 $ 12

Income Tax

Income Tax	3 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax	I. Income Tax Effective Tax Rate Three Months Ended December 31 2019 2018 (Dollars in millions) (Provision) benefit for income taxes $ (4 ) $ 7 Effective tax rate 7 % (10 )% For the three months ended December 31, 2019 Tax Reform On December 22, 2017, the U.S. enacted significant changes to federal income tax law affecting us, including a permanent reduction of the U.S. corporate income tax rate from 35% to 21%, effective January 1, 2018, as well as a 100% dividend received deduction for foreign dividends. Although the passage of the Act reduced the U.S. tax rate and effectively created a participation exemption regime for foreign earnings, certain other aspects of the new legislation, including in particular, immediate U.S. taxation of global intangible low-taxed income (“GILTI”) earned by foreign subsidiaries, had a negative impact on earnings and this is one of the primary drivers of the increase in Cabot’s effective tax rate, prior to consideration of the discrete tax benefits. Uncertainties Cabot and certain subsidiaries are under audit in a number of jurisdictions. In addition, certain statutes of limitations are scheduled to expire in the near future. It is reasonably possible that a further change in the unrecognized tax benefits may also occur within the next twelve months related to the settlement of one or more of these audits or the lapse of applicable statutes of limitations. However, an estimated range of the impact on the unrecognized tax benefits cannot be quantified at this time. Cabot files U.S. federal and state and non-U.S. income tax returns in jurisdictions with varying statutes of limitations. The 2016 through 2019 tax years generally remain subject to examination by the IRS and various tax years from 2005 through 2019 remain subject to examination by the respective state tax authorities. In significant non-U.S. jurisdictions, various tax years from 2003 through 2019 remain subject to examination by their respective tax authorities. As of December 31, 2019, Cabot’s significant non-U.S. jurisdictions include Canada, China, France, Germany, Italy, Japan, Switzerland and the Netherlands. During the three months ended December 31, 2019, Cabot released uncertain tax positions of $6 million due to the expiration of statutes of limitations in various jurisdictions

Earnings Per Share

Earnings Per Share	3 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	J. Earnings Per Share The following tables summarize the components of the basic and diluted earnings (loss) per common share (“EPS”) computations: Three Months Ended December 31 2019 2018 (In millions, except per share amounts) Basic EPS: Net income (loss) attributable to Cabot Corporation $ 41 $ 69 Less: Undistributed earnings allocated to participating securities (1) — — Earnings (loss) allocated to common shareholders (numerator) $ 41 $ 69 Weighted average common shares and participating securities outstanding 57.7 60.8 Less: Participating securities (1) 0.8 0.9 Adjusted weighted average common shares (denominator) 56.9 59.9 Earnings (loss) per common share - basic: $ 0.71 $ 1.14 Diluted EPS: Earnings (loss) allocated to common shareholders $ 41 $ 69 Plus: Earnings (loss) allocated to participating securities — 1 Less: Adjusted earnings allocated to participating securities (2) — 1 Earnings (loss) allocated to common shareholders (numerator) $ 41 $ 69 Adjusted weighted average common shares outstanding 56.9 59.9 Effect of dilutive securities: Common shares issuable (3) 0.1 0.2 Adjusted weighted average common shares (denominator) 57.0 60.1 Earnings (loss) per common share - diluted: $ 0.70 $ 1.14 (1) Undistributed earnings are the earnings which remain after dividends declared during the period are assumed to be distributed to the common and participating shareholders. Undistributed earnings are allocated to common and participating shareholders on the same basis as dividend distributions. The calculation of undistributed earnings is as follows: Three Months Ended December 31 2019 2018 (In millions) Calculation of undistributed earnings (loss): Net income (loss) attributable to Cabot Corporation $ 41 $ 69 Less: Dividends declared on common stock 20 20 Undistributed earnings (loss) $ 21 $ 49 Allocation of undistributed earnings (loss): Undistributed earnings (loss) allocated to common shareholders $ 21 $ 49 Undistributed earnings (loss) allocated to participating shareholders — — Undistributed earnings (loss) $ 21 $ 49 (2) Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (3) below, and then reallocated to participating securities. (3) Represents incremental shares of common stock from the (i) assumed exercise of stock options issued under Cabot’s equity incentive plans; and (ii) assumed issuance of shares to employees pursuant to the Company’s Deferred Compensation and Supplemental Retirement Plan. For the three months ended December 31, 2019, 995,294 incremental shares of common stock were excluded from the calculation of diluted earnings per share because the inclusion of these shares would have been antidilutive. For the three months ended December 31, 2018, 687,995 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.

Restructuring

Restructuring	3 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Restructuring	K. Restructuring Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations in the three months ended December 31, 2019 and 2018 as follows: Three Months Ended December 31 2019 2018 (In millions) Cost of sales $ 1 $ 3 Selling and administrative expenses 7 6 Total $ 8 $ 9 Details of all restructuring activities and the related reserves during the three months ended December 31, 2019 were as follows: Severance and Employee Benefits Environmental Remediation Other Total (In millions) Reserve at September 30, 2019 $ 3 $ 4 $ — $ 7 Charges (gain) 7 — 1 8 Cash paid (2 ) — (1 ) (3 ) Reserve at December 31, 2019 8 4 — 12 Cabot’s severance and employee benefit reserves and other closure related reserves are reflected in Accounts payable and accrued liabilities on the Company’s Consolidated Balance Sheets. Cabot’s environmental remediation reserves related to restructuring activities are reflected in Other liabilities on the Company’s Consolidated Balance Sheets. 2020 Reorganization During the first quarter of fiscal 2020, the Company initiated several actions that it believes will enable the Company to perform certain activities more cost-effectively. These actions primarily consist of the reorganization of Cabot’s leadership structure, the creation of a Global Business Services function and other operational efficiency initiatives. As part of the creation of the Global Business Services function, certain business service activities performed at Cabot’s North American business service center will be consolidated into the Company’s European business service center. During the three months ended December 31, 2019, the Company recorded charges of $7 million in the aggregate for these actions, primarily related to severance costs. The Company expects to record additional restructuring charges of approximately $4 million, primarily related to severance costs, in the remainder of fiscal 2020 and thereafter. Cabot paid approximately $1 million related to these activities in the three months ended December 31, 2019 and expects to pay approximately $10 million in the remainder of fiscal 2020 and thereafter. As of December 31, 2019, Cabot had $6 million of accrued severance charges in the Consolidated Balance Sheets related to these actions. Purification Solutions Transformation Plan In December 2018, the Company initiated a transformation plan to improve the long-term performance of the Purification Solutions segment. The purpose of the plan is to focus the business’s product portfolio, optimize its manufacturing assets, and streamline its organizational structure to support the new focus. The Company expects to record total charges of $10 million related to this plan, of which approximately $9 million was recorded in fiscal 2019, comprised of severance, employee benefits and professional service fees. The Company recorded charges of less than $1 million and $8 million in the three months ended December 31, 2019 and 2018, respectively. The Company expects to record immaterial charges related to this plan through the rest of fiscal 2020. Cabot paid $8 million related to these activities through December 31, 2019, the majority of which was paid in fiscal 2019, and expects to pay approximately $1 million in the remainder of fiscal 2020. As of December 31, 2019, Cabot had $1 million of accrued severance charges in the Consolidated Balance Sheets related to these actions.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	3 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	L. Financial Instruments and Fair Value Measurements The FASB authoritative guidance on fair value measurements defines fair value, provides a framework for measuring fair value, and requires certain disclosures about fair value measurements. The required disclosures focus on the inputs used to measure fair value. The guidance establishes the following hierarchy for categorizing these inputs: Level 1 — Quoted market prices in active markets for identical assets or liabilities Level 2 — Significant other observable inputs (e.g., quoted prices for similar items in active markets, quoted prices for identical or similar items in markets that are not active, inputs other than quoted prices that are observable such as interest rate and yield curves, and market-corroborated inputs) Level 3 — Significant unobservable inputs There were no transfers of financial assets or liabilities measured at fair value between Level 1 and Level 2 and there were no Level 3 investments during the first three months of either fiscal 2020 or 2019. At December 31, 2019 and September 30, 2019, Cabot had derivatives relating to foreign currency risks, including a net investment hedge and forward foreign currency contracts, carried at fair value. At December 31, 2019, the fair value of these derivatives was a net liability of $3 million and was included in Prepaid expenses and other current assets, Accounts payable and accrued liabilities, and Other liabilities on the Consolidated Balance Sheets. At September 30, 2019, the fair value of these derivatives was a net asset of $1 million and was included in Prepaid expenses and other current assets and Other assets on the Consolidated Balance Sheets. These derivatives are classified as Level 2 instruments within the fair value hierarchy as the fair value determination was based on observable inputs. At December 31, 2019 and September 30, 2019, the fair value of guaranteed investment contracts, included in Other assets on the Consolidated Balance Sheets, was $11 million and $10 million, respectively. Guaranteed investment contracts were classified as Level 2 instruments within the fair value hierarchy as the fair value determination was based on other observable inputs. At December 31, 2019 and September 30, 2019, the fair values of cash and cash equivalents, accounts and notes receivable, accounts payable and accrued liabilities, and short-term borrowings and variable rate debt approximated their carrying values due to the short-term nature of these instruments. The carrying value and fair value of the long-term fixed rate debt were $1.08 billion and $1.14 billion, respectively, as of December 31, 2019, and $1.03 billion and $1.10 billion, respectively, as of September 30, 2019. The fair values of Cabot’s fixed rate long-term debt are estimated based on comparable quoted market prices at the respective period ends. The carrying amounts of Cabot’s floating rate long-term debt and capital lease obligations approximate their fair values. All such measurements are based on observable inputs and are classified as Level 2 within the fair value hierarchy. The valuation technique used is the discounted cash flow model.

Derivatives

Derivatives	3 Months Ended
	Dec. 31, 2019
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivatives	M. Derivatives Foreign Currency Risk Management Cabot’s international operations are subject to certain risks, including currency exchange rate fluctuations and government actions. Cabot endeavors to match the currency in which debt is issued to the currency of the Company’s major, stable cash receipts. In some situations, Cabot has issued debt denominated in U.S. dollars and then entered into cross-currency swaps that exchange the dollar principal and interest payments into Euro-denominated principal and interest payments. Additionally, the Company has foreign currency exposure arising from its net investments in foreign operations. Cabot may enter into cross-currency swaps to mitigate the impact of currency rate changes on the Company’s net investments. The Company also has foreign currency exposure arising from the denomination of monetary assets and liabilities in foreign currencies other than the functional currency of a given subsidiary as well as the risk that currency fluctuations could affect the dollar value of future cash flows generated in foreign currencies. Accordingly, Cabot uses short-term forward contracts to minimize the exposure to foreign currency risk. In certain situations where the Company has forecasted purchases under a long-term commitment or forecasted sales denominated in a foreign currency, Cabot may enter into appropriate financial instruments in accordance with the Company’s risk management policy to hedge future cash flow exposures. The following table provides details of the derivatives held as of December 31, 2019 and September 30, 2019 to manage foreign currency risk. Notional Amount Description Borrowing December 31, 2019 September 30, 2019 Hedge Designation Cross-Currency Swaps 3.4% Notes USD 250 million swapped to EUR 223 million USD 250 million swapped to EUR 223 million Net investment Forward Foreign Currency Contracts (1) N/A USD 43 million USD 54 million No designation (1) Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna. Accounting for Derivative Instruments and Hedging Activities The Company determines the fair value of financial instruments using quoted market prices whenever available. When quoted market prices are not available for various types of financial instruments (such as forwards, options and swaps), 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. Fair Value Hedge For derivative instruments that are designated and qualify as fair value hedges, the gain or loss on the derivative as well as the offsetting gain or loss on the hedged item attributable to the hedged risk are recognized in current period earnings. Cash Flow Hedge For derivative instruments that are designated and qualify as cash flow hedges, the effective portion of the gain or loss on the derivative is recorded in AOCI and reclassified to earnings in the same period or periods during which the hedged transaction affects earnings. Gains and losses on the derivative representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current period earnings. 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 foreign currency translation gains or losses in AOCI while changes in the ineffective portion are reported in earnings. Effectiveness is assessed using the method based on changes in spot exchange rates. 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. The Company has cross-currency swaps with a notional amount of $250 million, which are designated as hedges of its net investments in certain Euro-denominated subsidiaries. Cash settlements occur semi-annually on March 15 th th The following table summarizes the impact of the cross-currency swaps to AOCI and the Consolidated Statements of Operations: Three Months Ended December 31 2019 2018 2019 2018 2019 2018 Description Gain/(Loss) Recognized in AOCI (Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations (Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing) (In millions) Cross-currency swaps $ (4 ) $ 8 $ (1 ) $ (1 ) $ — $ — Other Derivative Instruments From time to time, the Company may enter into certain derivative instruments that may not be designated as hedges for accounting purposes, which may include cross-currency swaps, foreign currency forward contracts and commodity derivatives. For cross-currency swaps and foreign currency forward contracts not designated as hedges, the Company uses standard models with market-based inputs. The significant inputs to these models are interest rate curves for discounting future cash flows, and exchange rate curves of the foreign currency for translating future cash flows. In determining the fair value of the commodity derivatives, the significant inputs to valuation models are quoted market prices of similar instruments in active markets. Although these derivatives do not qualify for hedge accounting, Cabot believes that such instruments are closely correlated with the underlying exposure, thus managing the associated risk. The gains or losses from changes in the fair value of derivative instruments that are not accounted for as hedges are recognized in current period earnings. At both December 31, 2019 and September 30, 2019, the fair value of derivative instruments not designated as hedges were immaterial, and these instruments were presented in Prepaid expenses and other current assets and Accounts payable and accrued liabilities on the Consolidated Balance Sheets.

Financial Information by Segmen

Financial Information by Segment	3 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Financial Information by Segment	N. Financial Information by Segment The Company identifies a business as an operating segment if: (i) it engages in business activities from which it may earn revenues and incur expenses; (ii) its operating results are regularly reviewed by the Chief Operating Decision Maker (“CODM”), who is Cabot’s President and Chief Executive Officer, to make decisions about resources to be allocated to the segment and assess its performance; and (iii) it has available discrete financial information. The Company has determined that all of its businesses are operating segments. The CODM reviews financial information at the operating segment level to allocate resources and to assess the operating results and financial performance for each operating segment. Operating segments are aggregated into a reportable segment if the operating segments are determined to have similar economic characteristics and if the operating segments are similar in the following areas: (i) nature of products and services; (ii) nature of production processes; (iii) type or class of customer for their products and services; (iv) methods used to distribute the products or provide services; and (v) if applicable, the nature of the regulatory environment. The Company has three reportable segments: Reinforcement Materials, Performance Chemicals and Purification Solutions. The Company’s former Specialty Fluids business was a separate reporting segment. Since the Company divested this business in the third quarter of fiscal 2019, Cabot has been organized into the three reporting business segments named above. The Reinforcement Materials segment consists of the rubber blacks and elastomer composites product lines. The Performance Chemicals segment combines the specialty carbons, fumed metal oxides and aerogel product lines into the Performance Additives business, and combines the specialty compounds and inkjet colorants product lines into the Formulated Solutions business. These businesses are similar in terms of economic characteristics, nature of products, processes, customer class and product distribution methods, and, therefore, have been aggregated into one reportable segment. The net sales from each of these businesses for the three months ended December 31, 2019 and 2018 were as follows: Three Months Ended December 31 2019 2018 (In millions) Performance Additives $ 170 $ 167 Formulated Solutions 72 64 Total Performance Chemicals $ 242 $ 231 The Purification Solutions segment consists of the Company’s activated carbon business, and the Specialty Fluids segment included the Company’s former cesium formate oil and gas drilling fluids and high-purity fine cesium chemicals product lines. Income (loss) from continuing operations before income taxes (“Segment EBIT”) is presented for each reportable segment in the table below. Segment EBIT excludes Interest expense, general unallocated income (expense), unallocated corporate costs, and certain items, meaning items management does not consider representative of on-going operating segment results. In addition, Segment EBIT includes Equity in earnings of affiliated companies, net of tax, the full operating results of a contractual joint venture in Purification Solutions, royalties, Net income attributable to noncontrolling interests, net of tax, and discounting charges for certain Notes receivable. Financial information by reportable segment is as follows: Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids (1) Segment Total Unallocated and Other (2) Consolidated Total (In millions) Three Months Ended December 31, 2019 Revenues from external customers (3) $ 379 $ 242 $ 59 $ — $ 680 $ 47 $ 727 Income (loss) from continuing operations before income taxes (4) $ 47 $ 41 $ (2 ) $ — $ 86 $ (36 ) $ 50 Three Months Ended December 31, 2018 Revenues from external customers (3) $ 457 $ 231 $ 65 $ 19 $ 772 $ 49 $ 821 Income (loss) from continuing operations before income taxes (4) $ 62 $ 36 $ (3 ) $ 10 $ 105 $ (35 ) $ 70 ( 1 ) (2) ( 3 ) Consolidated Total Revenues from external customers reconciles to Net sales and other operating revenues on the Consolidated Statements of Operations. Revenues from external customers that are categorized as Unallocated and Other reflects royalties, external shipping and handling fees, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate , discounting charges for certain Notes receivable , and by-product revenue . Details are provided in the table below: Three Months Ended December 31 2019 2018 (In millions) Royalties, the impact of unearned revenue, the removal of 100% of the sales of an equity method affiliate and discounting charges for certain notes receivable $ (1 ) $ (3 ) Shipping and handling fees 31 32 By-product sales 17 20 Total $ 47 $ 49 ( 4 ) Consolidated Total Income (loss) from continuing operations before income taxes Three Months Ended December 31 2019 2018 (In millions) Interest expense $ (14 ) $ (15 ) Certain items (a) Global restructuring activities (Note K) (8 ) (9 ) Legal and environmental matters and reserves 1 — Employee benefit plan settlements (2 ) 3 Acquisition and integration-related charges (1 ) (3 ) Other (1 ) (1 ) Total certain items, pre-tax (11 ) (10 ) Unallocated corporate costs (b) (10 ) (12 ) General unallocated income (expense) (c) (1 ) 2 Less: Equity in earnings of affiliated companies, net of tax (d) — — Total $ (36 ) $ (35 ) (a) Certain items are (b) Unallocated corporate costs are costs that are not controlled by the segments and primarily benefit corporate interests. (c) General unallocated income (expense) consists of gains (losses) arising from foreign currency transactions, net of other foreign currency risk management activities, Interest and dividend income, the profit or loss related to the corporate adjustment for unearned revenue, the impact of including the full operating results of a contractual joint venture in Purification Solutions Segment EBIT and unrealized holding gains (losses) for equity securities. (d) Equity in earnings of affiliated companies, net of tax, is included in Segment EBIT and is removed in Unallocated and other to reconcile to Income (loss) from operations before income taxes and equity in earnings from affiliated companies. The Company’s segments operate globally. In addition to presenting Revenue from external customers by reportable segment, the following tables further disaggregate Revenues from external customers by geographic region. Three Months Ended December 31, 2019 Reinforcement Materials Performance Chemicals Purification Solutions Consolidated Total (In millions) Americas $ 141 $ 76 $ 26 $ 243 Asia Pacific 170 94 9 273 Europe, Middle East and Africa 68 72 24 164 Segment revenues from external customers 379 242 59 680 Unallocated and other 47 Net sales and other operating revenues $ 727 Three Months Ended December 31, 2018 Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids Consolidated Total (In millions) Americas $ 167 $ 72 $ 29 $ 2 $ 270 Asia Pacific 202 85 9 1 297 Europe, Middle East and Africa 88 74 27 16 205 Segment revenues from external customers 457 231 65 19 772 Unallocated and other 49 Net sales and other operating revenues $ 821

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition Cabot recognizes revenue when its customers obtain control of promised goods or services. The revenue recognized is the amount of consideration that the Company expects to receive in exchange for those goods or services. The Company’s contracts with customers are generally for products only and do not include other performance obligations. Generally, Cabot considers purchase orders, which in some cases are governed by master supply agreements, to be contracts with customers. The transaction price as specified on the purchase order or sales contract is considered the standalone selling price for each distinct product. To determine the transaction price at the time when revenue is recognized, the Company evaluates whether the price is subject to adjustments, such as for returns, discounts or volume rebates, which are stated in the customer contract, to determine the net consideration to which the Company expects to be entitled. Revenue from product sales is recognized based on a point in time model when control of the product is transferred to the customer, which typically occurs upon shipment or delivery of the product to the customer and title, risk and rewards of ownership have passed to the customer. The Company has an immaterial amount of revenue that is recognized over time. Payment terms typically range from zero to ninety days. Shipping and handling costs incurred after the transfer of control of a product to the customer are billed to the customer and are recorded as sales revenue, as the Company considers these to be fulfillment costs. Shipping and handling costs are expensed in the period incurred and included in Cost of sales within the Consolidated Statement of Operations. Taxes collected on sales to customers are excluded from the transaction price. The Company generally provides a warranty that its products will substantially conform to the identified specifications. The Company’s liability typically is limited to either a credit equal to the purchase price or replacement of the non-conforming product. Returns under warranty have historically been immaterial. The Company does not have contract assets or liabilities that are material. As permitted by the FASB’s revenue recognition standard, Revenue from Contracts with Customers , when the period of time between the transfer of control of the goods and the time the customer pays for the goods is one year or less, the Company does not consider there to be a significant financing component associated with the contract.
Intangible Assets and Goodwill Impairment	Intangible Assets and Goodwill Impairment The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for assets acquired and liabilities assumed in an acquisition are allocated to the assets and liabilities based on their fair values at the date of acquisition. The Company uses assumptions and estimates in determining the fair value of assets acquired and liabilities assumed in a business combination. The determination of the fair value of intangible assets requires the use of significant judgment with regard to assumptions used in the valuation model. The Company estimates the fair value of identifiable acquisition-related intangible assets principally based on projections of cash flows that will arise from these assets. The projected cash flows are discounted to determine the fair value of the assets at the dates of acquisition. Definite-lived intangible assets, which are comprised of trademarks, customer relationships and developed technologies, are amortized over their estimated useful lives and are reviewed for impairment when indication of potential impairment exists, such as a significant reduction in cash flows associated with the assets. Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value assigned to the net tangible and identifiable intangible assets acquired. Goodwill is not amortized, but is reviewed for impairment annually as of August 31, or when events or changes in the business environment indicate that the carrying value of the reporting unit may exceed its fair value. A reporting unit, for the purpose of the impairment test, is at or below the operating segment level, and constitutes a business for which discrete financial information is available and regularly reviewed by segment management. Reinforcement Materials, and the fumed metal oxides and specialty compounds product lines within Performance Chemicals, which are considered separate reporting units, carry the Company’s goodwill balances as of December 31, 2019. For the purpose of the goodwill impairment test, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If an initial qualitative assessment identifies that it is more likely than not that the carrying value of a reporting unit exceeds its estimated fair value, an additional quantitative evaluation is performed. Alternatively, the Company may elect to proceed directly to the quantitative goodwill impairment test. If based on the quantitative evaluation the fair value of the reporting unit is less than its carrying amount, a goodwill impairment loss would result. The goodwill impairment loss would be the amount by which the carrying value of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. The fair value of a reporting unit is based on discounted estimated future cash flows. The fair value is also benchmarked against a market approach using the guideline public company method. The assumptions used to estimate fair value include management’s best estimates of future growth rates, operating cash flows, capital expenditures and discount rates over an estimate of the remaining operating period at the reporting unit level. Based on the Company’s most recent annual goodwill impairment test performed as of August 31, 2019, the fair values of the Reinforcement Materials, Fumed Metal Oxides and Specialty Compounds reporting units were substantially in excess of their carrying values.
Long-Lived Assets Impairment	Long-lived Assets Impairment The Company’s long-lived assets primarily include property, plant and equipment, intangible assets and long-term investments. The carrying values of long-lived assets are reviewed for impairment whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. To test for impairment of assets, the Company generally uses a probability-weighted estimate of the future undiscounted net cash flows of the assets over their remaining lives to determine if the value of the asset is recoverable. Long-lived assets are grouped with other assets and liabilities at the lowest level for which independent identifiable cash flows are determinable. An asset impairment is recognized when the carrying value of the asset is not recoverable based on the analysis described above, in which case the asset is written down to its fair value. If the asset does not have a readily determinable fair value, a discounted cash flow model may be used to determine the fair value of the asset. In circumstances when an asset does not have separately identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset. The Company continues to consider strategic options for its Purification Solutions business. Depending on the actions taken, there could be a negative impact on the fair value of the Purification Solutions reporting unit, which may lead to an impairment.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives of the related assets. The depreciable lives for buildings, machinery and equipment, and other fixed assets are between twenty and twenty-five years, ten and twenty-five years, and three and twenty-five years, respectively. The cost and accumulated depreciation for property, plant and equipment sold, retired, or otherwise disposed of are removed from the Consolidated Balance Sheets and resulting gains or losses are included in earnings in the Consolidated Statements of Operations. Expenditures for repairs and maintenance are charged to expenses as incurred. Expenditures for major renewals and betterments, which significantly extend the useful lives of existing plant and equipment, are capitalized and depreciated.
Income Tax in Interim Periods	Income Tax in Interim Periods The Company records its tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period. Valuation allowances are provided against the future tax benefits that arise from the deferred tax assets in jurisdictions for which no benefit can be recognized. The estimated annual effective tax rate may be significantly impacted by nondeductible expenses and the Company’s projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised.
Inventory Valuation	Inventory Valuation Inventories are stated at the lower of cost or net realizable value. The cost of inventory is determined using the FIFO method. Cabot periodically reviews inventory for both potential obsolescence and potential declines in anticipated selling prices. In this review, the Company makes assumptions about the future demand for and market value of the inventory, and based on these assumptions estimates the amount of any obsolete, unmarketable, slow moving, or overvalued inventory. Cabot writes down the value of these inventories by an amount equal to the difference between the cost of the inventory and its estimated net realizable value.
Pensions and Other Postretirement Benefits	Pensions and Other Postretirement Benefits The Company recognizes the funded status of defined benefit pension and other postretirement benefit plans as an asset or liability. This amount is defined as the difference between the fair value of plan assets and the benefit obligation. Pension and post-retirement benefit costs other than service cost are included in Other income (expense) in the Consolidated Statement of Operations. The Company is required to recognize as a component of Other comprehensive income (loss), net of tax, the actuarial gains/losses and prior service costs/credits that arise but were not previously required to be recognized as components of net periodic benefit cost. Other comprehensive income (loss) is adjusted as these amounts are later recognized in income as components of net periodic benefit cost.
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Accumulated other comprehensive income (loss) (“AOCI”), which is included as a component of stockholders’ equity, includes unrealized gains or losses on derivative instruments, currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In February 2016, the FASB issued a new standard for the accounting for leases. This standard requires lessees to recognize assets and liabilities for most leases, but recognize expenses on their income statements in a manner that is similar to the historical accounting treatment for leases. The Company adopted the standard on October 1, 2019 using the modified retrospective optional transition method. Accordingly, leases in the prior period continue to be reported and disclosed in accordance with the Company’s historical accounting treatment. The Company elected the package of practical expedients that permits the Company to not reassess the identification, classification and initial direct costs of leases commencing before the October 1, 2019 effective date and to exclude short-term leases from the balance sheet. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases or the practical expedient to not separate lease and non-lease components to existing leases, as well as new leases, through transition. The Company allocates the total consideration to the lease components and non-lease components on an observable stand-alone price basis to all asset classes. Adoption of the new lease standard resulted in the recognition of operating lease right-of-use (“ROU”) assets and operating lease liabilities of approximately $106 million and $111 million, respectively, as of October 1, 2019. Refer to Note H for further details regarding the balance sheet classification of these items. The difference between the operating lease ROU assets and operating lease liabilities reflects the reclassification of historical deferred rent balances of approximately $ 5 million. The effects of transition to the new standard resulted in no cumulative adjustment to retained earnings in the period of adoption. The standard did not materially impact the Company’s Consolidated Statement of Operations or Consolidated Statement of Cash Flows. The new standard did not have a material impact on the Company’s liquidity or debt-covenant compliance under its current debt agreements. In February 2018, the FASB issued a new standard that allows entities to reclassify from AOCI to Retained earnings stranded tax effects resulting from changes made as a result of the Tax Cuts and Jobs Act of 2017 (the “Act”). The Company adopted this standard on October 1, 2019 which resulted in the reclassification of a $2 million net gain from AOCI to Retained earnings. The reclassification was primarily related to the Company’s pension plans and derivative instruments.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued a new standard on measurement of credit losses. The standard introduces an "expected loss" impairment model that applies to most financial assets measured at amortized cost and certain other instruments, including trade and other receivables and other financial assets. Entities are required to estimate expected credit losses over the life of financial assets and record an allowance against the assets’ amortized cost basis to present them at the amount expected to be collected. The new standard is effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The Company is evaluating this standard and the timing of its adoption. The Company does not expect the adoption of this standard to materially impact the Company’s consolidated financial statements.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs	Net periodic defined benefit pension and other postretirement benefit costs include the following: Three Months Ended December 31 2019 2018 2019 2018 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (In millions) Service cost $ — $ 1 $ — $ 2 $ — $ — $ — $ — Interest cost 1 1 1 2 — — — — Expected return on plan assets (1 ) (2 ) (2 ) (4 ) — — — — Amortization of prior service credit — — — — — — — — Amortization of actuarial loss — 1 — 1 — — — — Settlement and curtailment gain — — — (6 ) — — — — Net periodic benefit (credit) cost $ — $ 1 $ (1 ) $ (5 ) $ — $ — $ — $ —

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Dec. 31, 2019
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 three month period ended December 31, 2019 are as follows: Reinforcement Materials Performance Chemicals Total (In millions) Balance at September 30, 2019 $ 50 $ 40 $ 90 Foreign currency impact 1 1 2 Balance at December 31, 2019 $ 51 $ 41 $ 92
Schedule of Intangible Assets	The following table provides information regarding the Company’s intangible assets: December 31, 2019 September 30, 2019 Gross Carrying Value Accumulated Amortization Net Intangible Assets Gross Carrying Value Accumulated Amortization Net Intangible Assets (In millions) Intangible assets with finite lives Developed technologies $ 51 $ (5 ) $ 46 $ 50 $ (5 ) $ 45 Trademarks 8 — 8 8 — 8 Customer relationships 58 (15 ) 43 57 (14 ) 43 Total intangible assets $ 117 $ (20 ) $ 97 $ 115 $ (19 ) $ 96

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Changes in Each Component of AOCI, Net of Tax	Changes in each component of AOCI, net of tax, were as follows: Currency Translation Adjustment Unrealized Gains on Investments Pension and Other Postretirement Benefit Liability Adjustments Total (In millions) Balance at September 30, 2019, attributable to Cabot Corporation $ (338 ) $ 1 $ (54 ) $ (391 ) Other comprehensive income (loss) before reclassifications 43 — — 43 Amounts reclassified from AOCI (1 ) — 1 — Adoption of accounting standards (3 ) (1 ) 1 (3 ) Less: Other comprehensive income (loss) attributable to noncontrolling interests 3 — — 3 Balance at December 31, 2019, attributable to Cabot Corporation $ (302 ) $ — $ (52 ) $ (354 )
Amounts Reclassified Out of AOCI	The amounts reclassified out of AOCI and into the Consolidated Statements of Operations in the three months ended December 31, 2019 and 2018 were as follows: Affected Line Item in the Consolidated Three Months Ended December 31 Statements of Operations 2019 2018 (In millions) Derivatives: net investment hedges (Gains) losses reclassified to interest expense Interest expense $ (1 ) $ (1 ) Pension and other postretirement benefit liability adjustment Amortization of actuarial losses Net Periodic Benefit Cost - see Note D for details 1 1 Settlement and curtailment gain Net Periodic Benefit Cost - see Note D for details — (6 ) Total before tax — (6 ) Tax impact Provision (benefit) for income taxes — (3 ) Total after tax $ — $ (9 )

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Components of Purchase 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. For these purchase commitments, the amounts included in the table below are based on market prices at December 31, 2019, which may differ from actual market prices at the time of purchase. Payments Due by Fiscal Year Remainder of Fiscal 2020 2021 2022 2023 2024 Thereafter Total (In millions) Reinforcement Materials $ 174 $ 132 $ 117 $ 107 $ 106 $ 1,211 $ 1,847 Performance Chemicals 50 57 55 36 31 405 634 Purification Solutions 3 1 — — — — 4 Total $ 227 $ 190 $ 172 $ 143 $ 137 $ 1,616 $ 2,485

Leases (Tables)

Leases (Tables)	3 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Components of Company's Lease Costs	The components of the Company’s lease costs were as follows: Three Months Ended December 31 2019 (In millions) Operating lease cost $ 6 Finance lease cost 1 Total lease cost $ 7
Supplemental Cash Flow Information Related to Company's Leases	Supplemental cash flow information related to the Company’s leases was as follows: Three Months Ended December 31 2019 (In millions) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6 Right-of-use assets obtained in exchange for new operating lease liabilities $ 2 Right-of-use assets obtained in exchange for new finance lease liabilities $ 20
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 December 31, 2019 (In millions) Lease ROU assets: Operating Other assets $ 102 Finance Net property, plant and equipment 46 Total lease ROU assets $ 148 Lease liabilities: Current: Operating Accounts payable and accrued liabilities $ 20 Finance Current portion of long-term debt 3 Long-term: Operating Other liabilities 88 Finance Long-term debt 29 Total lease liabilities $ 140
Weighed Average Remaining Lease Term and Discount Rates	The following table presents the weighted-average remaining lease term and discount rates for the Company’s leases as of December 31, 2019: Description December 31, 2019 Weighted-average remaining lease term (years): Operating leases 16 Finance leases 13 Weighted-average discount rate: Operating leases 2.29 % Finance leases 4.55 %
Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases	Future minimum lease payments under non-cancelable operating and finance leases as of December 31, 2019 are as follows: Years Ended September 30 Operating leases Finance leases (In millions) Remainder of fiscal 2020 $ 17 $ 4 2021 14 4 2022 10 4 2023 9 4 2024 9 4 2025 and thereafter 69 25 Total lease payments 128 45 Less: imputed interest 20 13 Total $ 108 $ 32 The Company’s future minimum lease payments under noncancelable leases as of September 30, 2019 were as follows: Years Ended September 30 Operating leases Capital leases (In millions) 2020 $ 23 $ 3 2021 14 3 2022 9 3 2023 9 3 2024 8 2 2025 and thereafter 68 7 Total lease payments 131 21 Less: imputed interest — 9 Total $ 131 $ 12

Income Tax (Tables)

Income Tax (Tables)	3 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Effective Tax Rate	Effective Tax Rate Three Months Ended December 31 2019 2018 (Dollars in millions) (Provision) benefit for income taxes $ (4 ) $ 7 Effective tax rate 7 % (10 )%

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS)	The following tables summarize the components of the basic and diluted earnings (loss) per common share (“EPS”) computations: Three Months Ended December 31 2019 2018 (In millions, except per share amounts) Basic EPS: Net income (loss) attributable to Cabot Corporation $ 41 $ 69 Less: Undistributed earnings allocated to participating securities (1) — — Earnings (loss) allocated to common shareholders (numerator) $ 41 $ 69 Weighted average common shares and participating securities outstanding 57.7 60.8 Less: Participating securities (1) 0.8 0.9 Adjusted weighted average common shares (denominator) 56.9 59.9 Earnings (loss) per common share - basic: $ 0.71 $ 1.14 Diluted EPS: Earnings (loss) allocated to common shareholders $ 41 $ 69 Plus: Earnings (loss) allocated to participating securities — 1 Less: Adjusted earnings allocated to participating securities (2) — 1 Earnings (loss) allocated to common shareholders (numerator) $ 41 $ 69 Adjusted weighted average common shares outstanding 56.9 59.9 Effect of dilutive securities: Common shares issuable (3) 0.1 0.2 Adjusted weighted average common shares (denominator) 57.0 60.1 Earnings (loss) per common share - diluted: $ 0.70 $ 1.14 (1)
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: Three Months Ended December 31 2019 2018 (In millions) Calculation of undistributed earnings (loss): Net income (loss) attributable to Cabot Corporation $ 41 $ 69 Less: Dividends declared on common stock 20 20 Undistributed earnings (loss) $ 21 $ 49 Allocation of undistributed earnings (loss): Undistributed earnings (loss) allocated to common shareholders $ 21 $ 49 Undistributed earnings (loss) allocated to participating shareholders — — Undistributed earnings (loss) $ 21 $ 49 (2) Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (3) below, and then reallocated to participating securities. (3) Represents incremental shares of common stock from the (i) assumed exercise of stock options issued under Cabot’s equity incentive plans; and (ii) assumed issuance of shares to employees pursuant to the Company’s Deferred Compensation and Supplemental Retirement Plan. For the three months ended December 31, 2019, 995,294 incremental shares of common stock were excluded from the calculation of diluted earnings per share because the inclusion of these shares would have been antidilutive. For the three months ended December 31, 2018, 687,995 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.

Restructuring (Tables)

Restructuring (Tables)	3 Months Ended
	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Recorded Restructuring Activities	Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations in the three months ended December 31, 2019 and 2018 as follows: Three Months Ended December 31 2019 2018 (In millions) Cost of sales $ 1 $ 3 Selling and administrative expenses 7 6 Total $ 8 $ 9
Restructuring Activities and Related Reserves	Details of all restructuring activities and the related reserves during the three months ended December 31, 2019 were as follows: Severance and Employee Benefits Environmental Remediation Other Total (In millions) Reserve at September 30, 2019 $ 3 $ 4 $ — $ 7 Charges (gain) 7 — 1 8 Cash paid (2 ) — (1 ) (3 ) Reserve at December 31, 2019 8 4 — 12

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Dec. 31, 2019
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 December 31, 2019 and September 30, 2019 to manage foreign currency risk. Notional Amount Description Borrowing December 31, 2019 September 30, 2019 Hedge Designation Cross-Currency Swaps 3.4% Notes USD 250 million swapped to EUR 223 million USD 250 million swapped to EUR 223 million Net investment Forward Foreign Currency Contracts (1) N/A USD 43 million USD 54 million No designation (1) Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna.
Summary Impact of Cross-currency Swaps to AOCI and Consolidated Statements of Operations	The following table summarizes the impact of the cross-currency swaps to AOCI and the Consolidated Statements of Operations: Three Months Ended December 31 2019 2018 2019 2018 2019 2018 Description Gain/(Loss) Recognized in AOCI (Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations (Gain)/Loss Recognized in Interest Expense in the Consolidated Statements of Operations (Amount Excluded from Effectiveness Testing) (In millions) Cross-currency swaps $ (4 ) $ 8 $ (1 ) $ (1 ) $ — $ —

Financial Information by Segm_2

Financial Information by Segment (Tables)	3 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Performance Segment	The net sales from each of these businesses for the three months ended December 31, 2019 and 2018 were as follows: Three Months Ended December 31 2019 2018 (In millions) Performance Additives $ 170 $ 167 Formulated Solutions 72 64 Total Performance Chemicals $ 242 $ 231
Financial Information by Reportable Segment	Financial information by reportable segment is as follows: Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids (1) Segment Total Unallocated and Other (2) Consolidated Total (In millions) Three Months Ended December 31, 2019 Revenues from external customers (3) $ 379 $ 242 $ 59 $ — $ 680 $ 47 $ 727 Income (loss) from continuing operations before income taxes (4) $ 47 $ 41 $ (2 ) $ — $ 86 $ (36 ) $ 50 Three Months Ended December 31, 2018 Revenues from external customers (3) $ 457 $ 231 $ 65 $ 19 $ 772 $ 49 $ 821 Income (loss) from continuing operations before income taxes (4) $ 62 $ 36 $ (3 ) $ 10 $ 105 $ (35 ) $ 70 ( 1 ) (2) ( 3 ) Consolidated Total Revenues from external customers reconciles to Net sales and other operating revenues on the Consolidated Statements of Operations. Revenues from external customers that are categorized as Unallocated and Other reflects royalties, external shipping and handling fees, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate , discounting charges for certain Notes receivable , and by-product revenue . Details are provided in the table below: Three Months Ended December 31 2019 2018 (In millions) Royalties, the impact of unearned revenue, the removal of 100% of the sales of an equity method affiliate and discounting charges for certain notes receivable $ (1 ) $ (3 ) Shipping and handling fees 31 32 By-product sales 17 20 Total $ 47 $ 49 ( 4 ) Consolidated Total Income (loss) from continuing operations before income taxes Three Months Ended December 31 2019 2018 (In millions) Interest expense $ (14 ) $ (15 ) Certain items (a) Global restructuring activities (Note K) (8 ) (9 ) Legal and environmental matters and reserves 1 — Employee benefit plan settlements (2 ) 3 Acquisition and integration-related charges (1 ) (3 ) Other (1 ) (1 ) Total certain items, pre-tax (11 ) (10 ) Unallocated corporate costs (b) (10 ) (12 ) General unallocated income (expense) (c) (1 ) 2 Less: Equity in earnings of affiliated companies, net of tax (d) — — Total $ (36 ) $ (35 ) (a) Certain items are (b) Unallocated corporate costs are costs that are not controlled by the segments and primarily benefit corporate interests. (c) General unallocated income (expense) consists of gains (losses) arising from foreign currency transactions, net of other foreign currency risk management activities, Interest and dividend income, the profit or loss related to the corporate adjustment for unearned revenue, the impact of including the full operating results of a contractual joint venture in Purification Solutions Segment EBIT and unrealized holding gains (losses) for equity securities. (d) Equity in earnings of affiliated companies, net of tax, is included in Segment EBIT and is removed in Unallocated and other to reconcile to Income (loss) from operations before income taxes and equity in earnings from affiliated companies.
Revenues from External Customers by Geographic Region	The Company’s segments operate globally. In addition to presenting Revenue from external customers by reportable segment, the following tables further disaggregate Revenues from external customers by geographic region. Three Months Ended December 31, 2019 Reinforcement Materials Performance Chemicals Purification Solutions Consolidated Total (In millions) Americas $ 141 $ 76 $ 26 $ 243 Asia Pacific 170 94 9 273 Europe, Middle East and Africa 68 72 24 164 Segment revenues from external customers 379 242 59 680 Unallocated and other 47 Net sales and other operating revenues $ 727 Three Months Ended December 31, 2018 Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids Consolidated Total (In millions) Americas $ 167 $ 72 $ 29 $ 2 $ 270 Asia Pacific 202 85 9 1 297 Europe, Middle East and Africa 88 74 27 16 205 Segment revenues from external customers 457 231 65 19 772 Unallocated and other 49 Net sales and other operating revenues $ 821

Significant Accounting Polici_3

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	Oct. 01, 2019	Dec. 31, 2019
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 106	$ 102
Operating lease liability	111	$ 108
Reclassification of deferred rent balances	5
Cumulative adjustment to retained earnings	0
Reclassification of net gain from Accumulated other comprehensive income (loss) to retained earnings	$ 2
Minimum [Member]
Significant Accounting Policies [Line Items]
Payment terms		0 days
Minimum [Member] | Buildings [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		20 years
Minimum [Member] | Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		10 years
Minimum [Member] | Other Fixed Assets [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Payment terms		90 days
Maximum [Member] | Buildings [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years
Maximum [Member] | Machinery and Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years
Maximum [Member] | Other Fixed Assets [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment		25 years

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended
	Dec. 31, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
NSCC Carbon (Jiangsu) Co. Ltd [Member]
Business Acquisition [Line Items]
Acquisition date		Sep. 30, 2018
Business acquisition, purchase price		$ 8,000,000
Expected production commencement year		2021
Transition related costs				$ 2,000,000
NSCC Carbon (Jiangsu) Co. Ltd [Member] | Maximum [Member]
Business Acquisition [Line Items]
Transition related costs			$ 1,000,000
Shenzhen Sanshun Nano New Materials Co., Ltd [Member]
Business Acquisition [Line Items]
Business acquisition, purchase price	$ 115,000,000
Business acquisition, cash consideration	100,000,000
Business acquisition, debt assumed	$ 15,000,000

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - Pension Benefits [Member] - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 1
Expected return on plan assets	(1)	(2)
Net periodic benefit (credit) cost		(1)
Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2
Interest cost	1	2
Expected return on plan assets	(2)	(4)
Amortization of actuarial loss	1	1
Settlement and curtailment gain		(6)
Net periodic benefit (credit) cost	$ 1	$ (5)

Employee Benefit Plans - Additi

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

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 90
Foreign currency impact	2
Ending balance	92
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	50
Foreign currency impact	1
Ending balance	51
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	40
Foreign currency impact	1
Ending balance	$ 41

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 117	$ 115
Accumulated Amortization	(20)	(19)
Net Intangible Assets, finite lives	97	96
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	51	50
Accumulated Amortization	(5)	(5)
Net Intangible Assets, finite lives	46	45
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	8	8
Net Intangible Assets, finite lives	8	8
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	58	57
Accumulated Amortization	(15)	(14)
Net Intangible Assets, finite lives	$ 43	$ 43

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
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	$ 1	$ 1
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	12 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	19 years

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	Oct. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 1,134	$ 1,134	$ 1,279
Adoption of accounting standards	2
Ending Balance		1,152	1,276
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(338)	(338)
Other comprehensive income (loss) before reclassifications		43
Amounts reclassified from AOCI		(1)
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		3
Ending Balance		(302)
Unrealized Gains on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	1	1
Adoption of accounting standards		(1)
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(54)	(54)
Amounts reclassified from AOCI		1
Adoption of accounting standards		1
Ending Balance		(52)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (391)	(391)	(317)
Other comprehensive income (loss) before reclassifications		43
Amounts reclassified from AOCI			(9)
Adoption of accounting standards		(3)
Less: Other comprehensive income (loss) attributable to noncontrolling interests		3
Ending Balance		$ (354)	$ (320)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) - Amounts Reclassified Out of AOCI (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
(Gains) Losses Reclassified to Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (1)	$ (1)
Amortization of Actuarial Losses [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ 1	1
Settlement and Curtailment Gain [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		(6)
Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		(6)
Tax impact		(3)
Total after tax		$ (9)

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Components of Purchase Commitments (Detail) $ in Millions	Dec. 31, 2019USD ($)
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2020	$ 227
Payments Due by Fiscal Year 2021	190
Payments Due by Fiscal Year 2022	172
Payments Due by Fiscal Year 2023	143
Payments Due by Fiscal Year 2024	137
Payments Due Thereafter	1,616
Payments Due, Total	2,485
Reinforcement Materials [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2020	174
Payments Due by Fiscal Year 2021	132
Payments Due by Fiscal Year 2022	117
Payments Due by Fiscal Year 2023	107
Payments Due by Fiscal Year 2024	106
Payments Due Thereafter	1,211
Payments Due, Total	1,847
Performance Chemicals [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2020	50
Payments Due by Fiscal Year 2021	57
Payments Due by Fiscal Year 2022	55
Payments Due by Fiscal Year 2023	36
Payments Due by Fiscal Year 2024	31
Payments Due Thereafter	405
Payments Due, Total	634
Purification Solutions [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2020	3
Payments Due by Fiscal Year 2021	1
Payments Due, Total	$ 4

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Respirator Liabilities [Member]
Loss Contingencies [Line Items]
Respirator reserve	$ 34		$ 35
Cash payments for respirator reserves	1	$ 1
Environmental Matters [Member]
Loss Contingencies [Line Items]
Reserved for environmental matters	12		$ 13
Cash payments for environmental reserves	$ 2	$ 1

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019USD ($)
Minimum [Member]
Lessee Lease Description [Line Items]
Lease term	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lease term	15 years
Lease extension period	15 years
Short term lease costs	$ 1
Variable lease cost	$ 1
Maximum [Member] | Land [Member]
Lessee Lease Description [Line Items]
Lease term	70 years

Leases - Components of Company'

Leases - Components of Company's Lease Costs (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating lease cost	$ 6
Finance lease cost	1
Total lease cost	$ 7

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information Related to Company's Leases (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 6
Right-of-use assets obtained in exchange for new operating lease liabilities	2
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 20

Leases - Supplemental Balance S

Leases - Supplemental Balance Sheet Information Related to Company's Leases (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 01, 2019
Lease ROU assets:
Operating	$ 102	$ 106
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Finance	$ 46
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet
Total lease ROU assets	$ 148
Lease liabilities:
Operating	$ 20
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Finance	$ 3
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtCurrent
Operating	$ 88
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Finance	$ 29
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtNoncurrent
Total lease liabilities	$ 140

Leases - Weighed Average Remain

Leases - Weighed Average Remaining Lease Term and Discount Rates (Detail)	Dec. 31, 2019
Lease Cost [Abstract]
Operating leases	16 years
Finance leases	13 years
Operating leases	2.29%
Finance leases	4.55%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments Under Non-cancelable Operating and Finance Leases (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 01, 2019
Operating leases
Remainder of fiscal 2020	$ 17
2021	14
2022	10
2023	9
2024	9
2025 and thereafter	69
Total lease payments	128
Less: imputed interest	20
Operating lease liability	108	$ 111
Finance leases
Remainder of fiscal 2020	4
2021	4
2022	4
2023	4
2024	4
2025 and thereafter	25
Total lease payments	45
Less: imputed interest	13
Total	$ 32

Leases - Future Minimum Lease_2

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

Income Tax - Effective Tax Rate

Income Tax - Effective Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
(Provision) benefit for income taxes	$ (4)	$ 7
Effective tax rate	7.00%	(10.00%)

Income Tax - Additional Informa

Income Tax - Additional Information (Detail) - USD ($) $ in Millions	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 30, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Net discrete tax (benefits) charges related to tax settlements		$ (10)		$ (24)
Net tax benefit related to result of changes in non-us tax laws		6
Changes in uncertain tax positions		$ 4
Net tax benefit related to result of changes in us tax laws				$ 17
Income tax rate	21.00%				35.00%
Percentage of dividend received deduction for foreign dividends		100.00%
Uncertain tax positions from expirations of statute of limitations		$ 6	$ 7
Accrued uncertain tax position for potential settlement		$ 2
Earliest Tax Year [Member] | United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2016
Latest Tax Year [Member] | United States Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2019
State Tax Authorities [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2005
State Tax Authorities [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2019
Non-U.S. Jurisdictions [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2003
Non-U.S. Jurisdictions [Member] | Latest Tax Year [Member]
Income Taxes [Line Items]
Tax years remain subject to examination		2019

Earnings Per Share - Components

Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Basic EPS:
Net income (loss) attributable to Cabot Corporation	$ 41	$ 69
Earnings (loss) allocated to common shareholders (numerator)	$ 41	$ 69
Weighted average common shares and participating securities outstanding	57.7	60.8
Less: Participating securities	0.8	0.9
Adjusted weighted average common shares (denominator)	56.9	59.9
Earnings (loss) per common share - basic:	$ 0.71	$ 1.14
Diluted EPS:
Earnings (loss) allocated to common shareholders	$ 41	$ 69
Plus: Earnings (loss) allocated to participating securities		1
Less: Adjusted earnings allocated to participating securities		1
Earnings (loss) allocated to common shareholders (numerator)	$ 41	$ 69
Adjusted weighted average common shares outstanding	56.9	59.9
Common shares issuable	0.1	0.2
Adjusted weighted average common shares (denominator)	57	60.1
Earnings (loss) per common share - diluted:	$ 0.70	$ 1.14

Earnings Per Share - Calculatio

Earnings Per Share - Calculation of Undistributed Earnings (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income (loss) attributable to Cabot Corporation	$ 41	$ 69
Less: Dividends declared on common stock	20	20
Undistributed earnings (loss)	21	49
Undistributed earnings (loss) allocated to common shareholders	$ 21	$ 49

Earnings Per Share - Componen_2

Earnings Per Share - Components of Basic and Diluted Earnings (Loss) Per Common Share (EPS) (Parenthetical) (Detail) - shares	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share	995,294	687,995

Restructuring - Recorded Restru

Restructuring - Recorded Restructuring Activities (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 8	$ 9
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	1	3
Selling and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 7	$ 6

Restructuring - Restructuring A

Restructuring - Restructuring Activities and Related Reserves (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2019USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 7
Charges (gain)	8
Cash paid	(3)
Reserve balance	12
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	3
Charges (gain)	7
Cash paid	(2)
Reserve balance	8
Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges (gain)	1
Cash paid	(1)
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	4
Reserve balance	$ 4

Restructuring - Additional Info

Restructuring - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 30, 2018	Sep. 30, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ 8
2020 Reorganization [Member]
Restructuring Cost And Reserve [Line Items]
Severance costs	7
Restructuring charges expected remainder of fiscal 2020 and thereafter	4
Restructuring cash payments of fiscal year	1
Restructuring cash payments through the reminder of fiscal 2020 and thereafter	10
Accrued severance charges	6
Purification Solutions Transformation Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring cash payments of fiscal year	8
Accrued severance charges	1
Restructuring Charges	10	$ 8	$ 9
Restructuring cash payments through the reminder of fiscal 2020	1
Purification Solutions Transformation Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ 1

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, liabilities, Level 2 to Level 1 transfers, amount	$ 0	$ 0
Fair value, assets, Level 2 to Level 1 transfers, amount	0	0
Fair value, liabilities, Level 1 to Level 2 transfers, amount	0	0
Fair value, assets, Level 1 to Level 2 transfers, amount	0	0
Fair value, assets, transfers into Level 3, amount	0	0
Fair value, assets, transfers out of Level 3, amount	0	0
Fair value, liabilities, transfers into Level 3, amount	0	0
Fair value, liabilities, transfers out of Level 3, amount	0	$ 0
Fair value of long-term debt	1,140,000,000		$ 1,100,000,000
Fixed Rate Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt	1,080,000,000		1,030,000,000
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	11,000,000		10,000,000
Significant Observable Inputs (Level 2) [Member] | Foreign Currency Risks [Member] | Prepaid Expenses and Other Current Assets and Other Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities), at fair Value, net	$ (3,000,000)		$ 1,000,000

Derivatives - Details of Deriva

Derivatives - Details of Derivatives Held to Manage Foreign Currency Risk (Detail)		Dec. 31, 2019USD ($)	Dec. 31, 2019EUR (€)	Sep. 30, 2019USD ($)	Sep. 30, 2019EUR (€)
Net Investment Hedge [Member] | Cross Currency Swaps [Member]
Derivative [Line Items]
Notional Amount		$ 250,000,000
Net Investment Hedge [Member] | 3.4% Notes [Member] | Cross Currency Swaps [Member]
Derivative [Line Items]
Notional Amount		$ 250,000,000	€ 223,000,000	$ 250,000,000	€ 223,000,000
Net Investment Hedge [Member] | 3.4% Notes [Member] | Fixed Rate Debt [Member] | Cross Currency Swaps [Member]
Derivative [Line Items]
Interest rate on borrowing		3.40%	3.40%	3.40%	3.40%
Not Designated as Hedging Instrument [Member] | Forward Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional Amount	[1]	$ 43,000,000		$ 54,000,000
[1]	Cabot’s forward foreign exchange contracts are denominated in the Canadian dollar, Indonesian rupiah and Czech koruna.

Derivatives - Additional Inform

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

Derivatives - Summary Impact of

Derivatives - Summary Impact of Cross-currency Swaps to AOCI and Consolidated Statements of Operations (Detail) - Cross Currency Swaps [Member] - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) Recognized in AOCI	$ (4)	$ 8
(Gain)/Loss Reclassified from AOCI into Interest Expense in the Consolidated Statements of Operations	$ (1)	$ (1)

Financial Information by Segm_3

Financial Information by Segment - Additional Information (Detail) - Segment	3 Months Ended
	Dec. 31, 2019	Jun. 30, 2019
Segment Reporting Information [Line Items]
Number of business reportable segments	3	3
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Number of business reportable segments	1

Financial Information by Segm_4

Financial Information by Segment - Schedule of Performance Segment (Detail) - Performance Chemicals [Member] - Operating Segments [Member] - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net sales	$ 242	$ 231
Performance Additives [Member]
Segment Reporting Information [Line Items]
Net sales	170	167
Formulated Solutions [Member]
Segment Reporting Information [Line Items]
Net sales	$ 72	$ 64

Financial Information by Segm_5

Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues from external customers	$ 727	$ 821
Income (loss) from continuing operations before income taxes	50	70
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	680	772
Income (loss) from continuing operations before income taxes	86	105
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	47	49
Income (loss) from continuing operations before income taxes	(36)	(35)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	379	457
Income (loss) from continuing operations before income taxes	47	62
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	242	231
Income (loss) from continuing operations before income taxes	41	36
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	59	65
Income (loss) from continuing operations before income taxes	$ (2)	(3)
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers		19
Income (loss) from continuing operations before income taxes		$ 10

Financial Information by Segm_6

Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%

Financial Information by Segm_7

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable and By-product Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues from external customers	$ 727	$ 821
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	47	49
Unallocated and Other [Member] | Royalties, the Impact of Unearned Revenue, the Removal of 100% of the Sales of an Equity Method Affiliate and Discounting Charges for Certain Notes Receivable [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	(1)	(3)
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	31	32
Unallocated and Other [Member] | By-product Sales [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 17	$ 20

Financial Information by Segm_8

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable and By-product Revenue (Parenthetical) (Detail)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%

Financial Information by Segm_9

Financial Information by Segment - Schedule of Income (Loss) from Continuing Operations before Income Taxes and Equity in Earnings of Affiliated Companies for Unallocated and Other (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Interest expense	$ (14)	$ (15)
Global restructuring activities	(8)	(9)
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(14)	(15)
Unallocated corporate costs	(10)	(12)
General unallocated income (expense)	(1)	2
Income from continuing operations before income taxes and equity in earnings of affiliated companies	(36)	(35)
Certain Items [Member]
Segment Reporting Information [Line Items]
Global restructuring activities	(8)	(9)
Legal and environmental matters and reserves	1
Employee benefit plan settlements	(2)	3
Acquisition and integration-related charges	(1)	(3)
Other	(1)	(1)
Total certain items, pre-tax	$ (11)	$ (10)

Financial Information by Seg_10

Financial Information by Segment - Revenue from External Customers by Geographic Region (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 727	$ 821
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	680	772
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	47	49
Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	243	270
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	273	297
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	164	205
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	379	457
Reinforcement Materials [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	141	167
Reinforcement Materials [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	170	202
Reinforcement Materials [Member] | Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	68	88
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	242	231
Performance Chemicals [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	76	72
Performance Chemicals [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	94	85
Performance Chemicals [Member] | Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	72	74
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	59	65
Purification Solutions [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	26	29
Purification Solutions [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	9	9
Purification Solutions [Member] | Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues	$ 24	27
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		19
Specialty Fluids [Member] | Americas [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		2
Specialty Fluids [Member] | Asia Pacific [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		1
Specialty Fluids [Member] | Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Net sales and other operating revenues		$ 16