Cabot (CBT) 10-Q 5 Feb 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2015	Feb. 03, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Trading Symbol	CBT
Entity Registrant Name	CABOT CORP
Entity Central Index Key	16,040
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,358,741

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales and other operating revenues	$ 603	$ 812
Cost of sales	504	655
Gross profit	99	157
Selling and administrative expenses	71	78
Research and technical expenses	16	15
Income from operations	12	64
Interest and dividend income	1	1
Interest expense	(13)	(13)
Other expense	(8)	(1)
(Loss) income from continuing operations	(8)	51
Benefit (provision) for income taxes	5	(3)
Equity in earnings of affiliated companies, net of tax		1
Net (loss) income	(3)	49
Net income attributable to noncontrolling interests, net of tax	4	4
Net (loss) income attributable to Cabot Corporation	$ (7)	$ 45
Weighted-average common shares outstanding, in millions:
Basic	62.5	64.1
Diluted	62.5	64.6
Basic:
Net (loss) income attributable to Cabot Corporation	$ (0.11)	$ 0.70
Diluted:
Net (loss) income attributable to Cabot Corporation	(0.11)	0.69
Dividends per common share	$ 0.22	$ 0.22

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net (loss) income	$ (3)	$ 49
Other comprehensive loss, net of tax
Foreign currency translation adjustment (net of tax benefit of $- and $1)	(47)	(103)
Pension and other postretirement benefit liability adjustments
Pension and other postretirement benefit liability adjustments arising during the period (net of tax provision of $- and $6)	(1)	21
Other comprehensive loss	(48)	(82)
Comprehensive loss	(51)	(33)
Net income attributable to noncontrolling interests	4	4
Noncontrolling interests foreign currency translation adjustment, net of tax	(3)	(2)
Comprehensive income attributable to noncontrolling interests, net of tax	1	2
Comprehensive loss attributable to Cabot Corporation	$ (52)	$ (35)

Consolidated Statements of Com4

Consolidated Statements of Comprehensive (Loss) Income (Parenthetical) (Unaudited) $ in Millions	3 Months Ended
	Dec. 31, 2014USD ($)
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency translation adjustment, tax benefit	$ 1
Pension and other postretirement benefit liability adjustments arising during the period, tax provision	$ 6

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015
Current assets:
Cash and cash equivalents	$ 84	$ 77
Accounts and notes receivable, net of reserve for doubtful accounts of $8 and $7	437	477
Inventories:
Raw materials	65	69
Work in process	4	1
Finished goods	261	287
Other	39	40
Total inventories	369	397
Prepaid expenses and other current assets	66	54
Deferred income taxes	43	43
Total current assets	999	1,048
Property, plant and equipment, net	1,315	1,383
Goodwill	153	154
Equity affiliates	54	57
Intangible assets, net	149	153
Assets held for rent	90	86
Deferred income taxes	153	152
Other assets	42	42
Total assets	2,955	3,075
Current liabilities:
Notes payable	7	22
Accounts payable and accrued liabilities	376	389
Income taxes payable	24	28
Deferred income taxes	1	1
Current portion of long-term debt	301	1
Total current liabilities	709	441
Long-term debt	670	970
Deferred income taxes	59	59
Other liabilities	235	240
Redeemable preferred stock	$ 27	$ 27
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: 0 and 64,634,731 shares Outstanding: 0 and 64,382,366 shares	$ 63	$ 63
Less cost of 246,293 and 246,570 shares of common treasury stock	(8)	(8)
Retained earnings	1,448	1,478
Accumulated other comprehensive loss	(344)	(299)
Total Cabot Corporation stockholders' equity	1,159	1,234
Noncontrolling interests	96	104
Total stockholders' equity	1,255	1,338
Total liabilities and stockholders’ equity	$ 2,955	$ 3,075

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 8	$ 7
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	62,596,786	62,704,966
Common stock, outstanding shares	62,350,493	62,458,396
Common treasury stock, shares	246,293	246,570

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities:
Net (loss) income	$ (3)	$ 49
Adjustments to reconcile net (loss) income to cash provided by operating activities:
Depreciation and amortization	41	45
Long-lived asset impairment charge (Note J)	23
Deferred tax benefit		(7)
Employee benefit plan settlement		18
Equity in net income of affiliated companies		(1)
Non-cash compensation	3	4
Other non-cash (income) expense	8
Changes in assets and liabilities:
Accounts and notes receivable	30	23
Inventories	16	7
Prepaid expenses and other current assets	(13)	(2)
Accounts payable and accrued liabilities	(6)	(73)
Income taxes payable	(6)	(2)
Other liabilities	(13)	(14)
Cash dividends received from equity affiliates	3	3
Other		6
Cash provided by operating activities	83	56
Cash Flows from Investing Activities:
Additions to property, plant and equipment	(24)	(41)
Proceeds from the sale of land	7
Change in assets held for rent	(1)	(3)
Cash used in investing activities	(18)	(44)
Cash Flows from Financing Activities:
Repayments under financing arrangements	(3)	(3)
Increase (decrease) in notes payable, net		1
(Repayments of) proceeds from issuance of commercial paper, net	(11)	117
Repayments of long-term debt		(32)
Purchases of common stock	(14)	(47)
Proceeds from sales of common stock	1	2
Cash dividends paid to common stockholders	(14)	(14)
Cash (used in) provided by financing activities	(41)	24
Effects of exchange rate changes on cash	(17)	(15)
Increase in cash and cash equivalents	7	21
Cash and cash equivalents at beginning of period	77	67
Cash and cash equivalents at end of period	$ 84	$ 88

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	A. Basis of Presentation The consolidated financial statements 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 the fiscal year ended September 30, 2015 (“2015 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, 2015 and 2014. 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.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	B. Significant Accounting Policies Revenue Recognition and Accounts Receivable Cabot recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable and collectability is reasonably assured. Cabot generally is able to ensure that products meet customer specifications prior to shipment. If the Company is unable to determine that the product has met the specified objective criteria prior to shipment or if title has not transferred because of sales terms, the revenue is considered “unearned” and is deferred until the revenue recognition criteria are met. Shipping and handling charges related to sales transactions are recorded as sales revenue when billed to customers or included in the sales price. Taxes collected on sales to customers are excluded from revenues. The following table shows the relative size of the revenue recognized in each of the Company’s reportable segments. Three Months Ended December 31, 2015 2014 Reinforcement Materials 51 % 59 % Performance Chemicals 36 % 29 % Purification Solutions 12 % 10 % Specialty Fluids 1 % 2 % Cabot derives the substantial majority of its revenues from the sale of products in Reinforcement Materials and Performance Chemicals. Revenue from these products is typically recognized when the product is shipped and title and risk of loss have passed to the customer. The Company offers certain of its customers cash discounts and volume rebates as sales incentives. The discounts and volume rebates are recorded as a reduction in sales at the time revenue is recognized and are estimated based on historical experience and contractual obligations. Cabot periodically reviews the assumptions underlying its estimates of discounts and volume rebates and adjusts its revenues accordingly. Revenue in Purification Solutions is typically recognized when the product is shipped and title and risk of loss have passed to the customer. For major activated carbon injection systems projects, revenue is recognized using the percentage-of-completion method . Revenue in Specialty Fluids arises primarily from the rental of cesium formate. This revenue is recognized throughout the rental period based on the contracted rental terms. Customers are also billed and revenue is recognized, typically at the end of the job, for cesium formate product that is not returned. The Company also generates revenues from cesium formate sold outside of a rental process and revenue is recognized upon delivery of the fluid . Cabot maintains allowances for doubtful accounts based on an assessment of the collectability of specific customer accounts, the aging of accounts receivable and other economic information on both a historical and prospective basis. Customer account balances are charged against the allowance when it is probable the receivable will not be recovered. There were no material changes in the allowance for any of the years presented. There is no material off-balance sheet credit exposure related to customer receivable balances . Intangible Assets and Goodwill Impairment The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for an acquisition are allocated to the assets acquired and liabilities assumed based on their fair values at the date of acquisition. 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 May 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. The reporting units with goodwill balances are Reinforcement Materials, Purification Solutions, and Fumed Metal Oxides. The separate businesses included within Performance Chemicals are considered separate reporting units. As such, the goodwill balance relative to Performance Chemicals is recorded in the Fumed Metal Oxides reporting unit. 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 under the two-step impairment test. 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, the Company performs an analysis of the fair value of all assets and liabilities of the reporting unit. If the implied fair value of the reporting unit’s goodwill is determined to be less than its carrying amount, an impairment is recognized for the difference. 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 companies 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. Should the fair value of any of the Company’s reporting units decline below its carrying amount because of reduced operating performance, market declines, changes in the discount rate, or other conditions, charges for impairment may be necessary. Based on the Company’s most recent annual goodwill impairment test performed as of May 31, 2015, the fair values of the Reinforcement Materials and Fumed Metal Oxides reporting units were substantially in excess of their carrying values. The fair value of the Purification Solutions reporting unit was less than its carrying amount and an impairment was recorded in the third fiscal quarter of 2015. Due to the impairment recorded as of June 30, 2015 , the fair value of the Purification Solutions reporting unit was insignificantly higher than its carrying value as of the last impairment date. No events occurred subsequent to the last impairment evaluation that would suggest that it is more likely than not that the carrying values of any of our reporting units exceeded their fair value. Nonetheless, the future growth in the Purification Solutions segment is highly dependent on achieving the expected volumes and margins in the activated carbon based mercury removal business. These volumes and margins are highly dependent on demand for mercury removal products and the Company’s successful realization of its anticipated share of volumes in this business. The expected demand for mercury removal products significantly depends on: (1) the implementation and enforcement of environmental laws and regulations, particularly those that would require U.S. based coal-fired electric utilities to reduce the quantity of air pollutants they release, including mercury, to comply with the Mercury and Air Toxics Standards (“MATS”) issued by the U.S. Environmental Protection Agency (“EPA”) and (2) other factors such as the anticipated usage of activated carbon in the coal-fired energy units. The MATS regulation has been subject to legal challenge and, in June 2015, the U.S. Supreme Court held that the EPA unreasonably failed to consider costs in determining whether it is necessary and appropriate to regulate hazardous air pollutants , including mercury, emitted by coal-fired utilities, and remanded the case back to the United States Co urt of Appeals for the District of Columbia Circuit Court for further proceedings. On December 15, 2015, the D.C. Circuit Court ruled to keep the MATS regulation in place while the EPA works to address the cost analysis required by the U.S. Supreme Court’s decision. EPA has indicated that it will complete this work by April 2016. 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. The Company recognized an impairment on intangible assets associated with the Purification Solutions business in the third fiscal quarter of 2015 and no events have been subsequently identified that would require an additional impairment evaluation. Long-lived Assets Impairment The Company’s long-lived assets primarily include property, plant and equipment, intangible assets, long-term investments and assets held for rent. 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 market 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 separate identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset. Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives. The depreciable lives for buildings, machinery and equipment, and other fixed assets are twenty to twenty-five years, ten to twenty-five years, and three to 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 market. The cost of all carbon black inventories in the U.S. is determined using the last-in, first-out (“LIFO”) method. Had the Company used the first-in, first-out (“FIFO”) method instead of the LIFO method for such inventories, the value of those inventories would have been $ 28 million and $ 30 million higher as of December 31, 2015 and September 30, 2015, respectively. The cost of Specialty Fluids inventories, which are classified as assets held for rent, is determined using the average cost method. The cost of other U.S. and non-U.S. inventories is determined using the first-in, first-out (“FIFO”) method. Cabot 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. The Company is required to recognize as a component of other comprehensive income, 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 is adjusted as these amounts are later recognized in income as components of net periodic benefit cost. Accumulated Other Comprehensive (Loss) Income Accumulated other comp rehensive (loss) income , which is included as a component of stockholders’ equity, includes unrealized gains or losses on available-for-sale marketable securities and derivative instruments , currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments. Recent Accounting Pronouncements In May 2014, the FASB issued a new standard related to the “Revenue from Contracts with Customers” which amends the existing accounting standards for revenue recognition. The standard requires entities to recognize revenue when they transfer promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. This standard is applicable for fiscal years beginning after December 15, 201 7 and for interim periods within those years and early adoption is permitted for the fiscal years beginning after December 15, 2016 . The Company expects to adopt this standard on October 1, 201 8 . The Company is currently evaluating the impact the adoption of this standard may have on its consolidated financial statements . In April 2015, the FASB issued a new standard simplifying the presentation of debt issuance costs by requiring debt issuance costs to be presented as a reduction of the corresponding debt liability. This will make the presentation of debt issuance costs consistent with the presentation of debt discounts or premiums. This standard is applicable for fiscal years beginning after December 15, 2015 and for interim periods within those years and early adoption is permitted. The Company expects to adopt this standard on October 1, 2016. The adoption of this standard is not expected to materially impact the Company’s consolidated financial statements. In November 2015, the FASB issued a new standard that amends the existing accounting standard for Income Taxes and simplifies the presentation of deferred income taxes. This will require that deferred income tax assets and liabilities be classified as noncurrent on the balance sheet. This standard is applicable for fiscal years beginning after December 15, 2016 and for interim periods within those years and early adoption is permitted . The Company is evaluating this standard and the timing of its adoption . The adoption of this standard is not expected to materially impact the Company’s consolidated financial statements.

Employee Benefit Plans

Employee Benefit Plans	3 Months Ended
	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	C . Employee Benefit Plans Net periodic defined benefit pension and other postretirement benefit costs include the following: Three Months Ended December 31, 2015 2014 2015 2014 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (Dollars in millions) Service cost $ — $ 2 $ — $ 2 $ — $ — $ — $ — Interest cost 1 2 2 3 — — — — Expected return on plan assets (3 ) (3 ) (3 ) (4 ) — — — — Amortization of prior service credit — — — — (1) — (1 ) — Amortization of actuarial loss — 1 — 1 — — — — Settlement and curtailment cost (credit) — — — 18 (1 ) — — — Net periodic (credit) benefit cost $ (2 ) $ 2 $ (1 ) $ 20 $ (2 ) $ — $ (1 ) $ — Settlement of employee benefit plan Effective October 1, 2014, the Company transferred the defined benefit obligations and pension plan assets in one of its foreign defined benefit plans to a multi-employer plan. As a result of the transfer, a pre-tax charge of $ 18 million was recorded in the three months ended December 31, 201 4 as reflected in Settlement costs in the table above. The pre-tax charge consists of $ 27 million released from Accumulated other comprehensive (loss) income (“ AOCI ”) and $ 2 million of employer contributions at the time of the settlement, partially offset by an $ 11 million release of the pension liability. The settlement charge has been recorded primarily in Cost of sales in the Consolidated Statements of Operations.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	D . Goodwill and Intangible Assets Cabot had goodwill balances of $ 1 53 million and $ 154 million at December 31, 2015 and September 30, 2015 , respectively. 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 , 2015 are as follows: Reinforcement Materials Performance Chemicals Purification Solutions Total (Dollars in millions) Balance at September 30, 2015 $ 55 $ 9 $ 90 $ 154 Foreign currency impact (1 ) — — (1 ) Balance at December 31, 2015 $ 54 $ 9 $ 90 $ 153 The following table provides information regarding the Company’s intangible assets: December 31, 2015 September 30, 2015 Gross Carrying Value Accumulated Amortization Net Intangible Assets Gross Carrying Value Accumulated Amortization Net Intangible Assets (Dollars in millions) Intangible assets with finite lives Developed technologies $ 48 $ (2 ) $ 46 $ 48 $ (1 ) $ 47 Trademarks 15 — 15 16 — 16 Customer relationships 95 (7 ) 88 96 (6 ) 90 Total intangible assets $ 158 $ (9 ) $ 149 $ 160 $ (7 ) $ 153 Intangible assets are amortized over their estimated useful lives, which range from fourteen to twenty-five years, with a weighted average amortization period of approximately nineteen years. Amortization expense for the three months ended December 31 , 2015 and 2014 was $ 2 million and $ 4 million, respectively, and is included in Cost of sales and Selling and administrative expenses in the Consolidated Statements of Operations. Total amortization expense is estimated to be approximately $ 9 million each year for the next five fiscal years.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Stockholders' Equity	E . Stockholders’ Equity In fiscal 2007, the Board of Directors authorized Cabot to repurchase up to ten million shares of Cabot’s common stock in the open market or in privately negotiated transactions. This authorization did not have a set expiration date. During the first quarter of fiscal 2015, Cabot repurchased 925,700 shares of its common stock under this authorization. In January 2015, the Board of Directors authorized Cabot to repurchase up to five million shares of its common stock in the open market or in privately negotiated transactions and cancelled the previous authorization. Cabot has repurchased 1,594,300 shares of its common stock under this authorization. As of December 31 , 2015, 3,405,700 shares remain available for repurchase under the current authorization. The Company retired the repurchased shares and recorded the excess of the purchase price over par value to additional paid-in capital until such amount was reduced to zero and then charged the remainder against retained earnings. During the first three months of both fiscal 20 16 and 2015 , Cabot paid cash dividends of $ 0. 22 per share of common stock for a total of $ 14 million. Noncontrolling interest The following table illustrates the noncontrolling interest activity for the periods presented: 2015 2014 (Dollars in millions) Balance at September 30 $ 104 $ 122 Net income attributable to noncontrolling interests 4 4 Noncontrolling interest foreign currency translation adjustment (3 ) (2 ) Noncontrolling interest dividends (9 ) — Balance at December 31 $ 96 $ 124 The dividends declared during the three months ended December 31, 2015 were not paid during the period.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Dec. 31, 2015
Stockholders Equity Note [Abstract]
Accumulated Other Comprehensive Loss	F . Accumulated Other Comprehensive Loss Comprehensive income combines net (loss) income 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, are as follows: Currency Translation Adjustment Unrealized Gains on Investments Pension and Other Postretirement Benefit Liability Adjustments Total (Dollars in millions) Balance at September 30, 2015, attributable to Cabot Corporation $ (239 ) $ 2 $ (62 ) $ (299 ) Other comprehensive loss before reclassifications (47 ) — — (47 ) Amounts reclassified from accumulated other comprehensive (loss) income — — (1 ) (1 ) Net other comprehensive items (286 ) 2 (63 ) (347 ) Less: Noncontrolling interest (3 ) — — (3 ) Balance at December 31, 2015, attributable to Cabot Corporation $ (283 ) $ 2 $ (63 ) $ (344 ) The amounts reclassified out of AOCI and into the Consolidated Statement s of Operations in the three months ended December 3 1 , 2015 and 2014 are as follows: Three Months Ended Affected Line Item in the Consolidated December 31, Statements of Operations 2015 2014 (Dollars in millions) Pension and other postretirement benefit liability adjustment Amortization of actuarial losses Net Periodic Benefit Cost - see Note C for details $ 1 $ 1 Amortization of prior service cost Net Periodic Benefit Cost - see Note C for details (1 ) (1 ) Settlement and curtailment (credit) cost Net Periodic Benefit Cost - see Note C for details (1 ) 27 Total before tax (1 ) 27 Tax impact Benefit for income taxes — (6 ) Total after tax $ (1 ) $ 21

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2015
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 those commitments, the amounts included in the table below are based on market prices at December 31 , 2015. Payments Due by Fiscal Year Remainder of Fiscal 2016 2017 2018 2019 2020 Thereafter Total (Dollars in millions) Reinforcement Materials $ 144 $ 136 $ 135 $ 132 $ 96 $ 1,702 $ 2,345 Performance Chemicals 44 50 37 32 29 155 347 Purification Solutions 10 7 1 — — — 18 Total $ 198 $ 193 $ 173 $ 164 $ 125 $ 1,857 $ 2,710 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, 201 5 and September 30, 2015 , Cabot had $ 15 million and $ 1 6 million, respectively, res erved for environmental matters . These environmental matters mainly relate to closed sites. These reserves 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 less than $ 1 million in the first three months of fiscal 2016 and 2015 , 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. Other Matters 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 2015 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. As of December 31 , 2015 and September 30, 201 5 , there were approximately 3 7 ,000 and 38 ,000 claimants, respectively, in pending cases asserting claims against AO in connection with respiratory products. Cabot has a reserve to cover its expected share of liability for existing and future respira tor liability claims. At December 31, 2015 and September 30, 2015 , the reserve was $ 10 million and $ 1 1 million, respectively. Cash payments related to this liability were $ 1 million in the f irst three months of both fiscal 201 6 and 201 5 . Other The Company has various other lawsuits, claims and contingent liabilities arising in the ordinary course of its business and with respect to the Company’s divested businesses. In the opinion of the Company, although final disposition of some or all of these other suits and claims may impact the Company’s consolidated financial statements in a particular period, they are not expected, in the aggregate, to have a material adverse effect on the Company’s consolidated financial statements .

Income Tax

Income Tax	3 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Tax	H . Income Tax Effective Tax Rate Three Months Ended December 31, 2015 2014 (Dollars in millions) (Benefit) Provision for income taxes $ (5 ) $ 3 Effective tax rate 74 % 5 % During the first quarter of fiscal 2016, the Company recorded a tax benefit of $ 5 million, resulting in an effective tax rate of 7 4 %. This amount included net discrete tax benefits of $ 6 million , primarily comprised of the net tax benefit from certain foreign exchange gains and losses, the renewal of the U.S. Research and Experimen tation credit and releases of reserves for uncertain tax positions . During the first quarter of fiscal 2015, the Company recorded a tax provision of $ 3 million, resulting in an effective tax rate of 5 %. This amount included net discrete tax benefits of $ 13 million , primarily comprised of the tax benefit from the change in accounting for uncertain tax positions, the renewal of the U.S. Research and Experimentation credit, and releases of reserves for uncertain tax positions . Uncertainties Cabot files U.S. federal and state and non-U.S. income tax returns in jurisdictions with varying statutes of limitations. The 2012 through 2015 tax years remain subject to examination by the United States Internal Revenue Service (“IRS”) and various tax years from 2005 through 2015 remain subject to examination by the respective state tax authorities. In significant non-U.S. jurisdictions, various tax years from 2004 through 2015 remain subject to examination by their respective tax authorities. Cabot’s significant non-U.S. jurisdictions include China, France, Germany, Italy, Japan, and the Netherlands. Certain Cabot subsidiaries are under audit in jurisdictions outside of the U.S. In addition, certain statutes of limitations are scheduled to expire in the near future. It is reasonably possible that a 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, however, an estimated range of the impact on the unrecognized tax benefits cannot be quantified at this time. During the three months ended December 31, 2015, Cabot released uncertain tax positions of $ 2 million due to the expirations of statutes of limitations in various jurisdictions.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	I . Earnings Per Share The following tables summarize the components of the basic and diluted earnings per common share computations: Three Months Ended December 31, 2015 2014 (Dollars and shares in millions, except per share amounts) Basic EPS: Net (loss) income attributable to Cabot Corporation $ (7 ) $ 45 Less: Dividends and dividend equivalents to participating securities — — Less: Undistributed earnings allocated to participating securities (1) — — (Loss) earnings allocated to common shareholders (numerator) $ (7 ) $ 45 Weighted average common shares and participating securities outstanding 62.9 64.6 Less: Participating securities (1) 0.4 0.5 Adjusted weighted average common shares (denominator) 62.5 64.1 Amounts per share - basic: Net (loss) income attributable to Cabot Corporation $ (0.11 ) $ 0.70 Diluted EPS (2) : (Loss) earnings allocated to common shareholders $ (7 ) $ 45 Plus: (Loss) earnings allocated to participating securities — — Less: Adjusted earnings allocated to participating securities (3) — — (Loss) earnings allocated to common shareholders (numerator) $ (7 ) $ 45 Adjusted weighted average common shares outstanding 62.5 64.1 Effect of dilutive securities: Common shares issuable (4) — 0.5 Adjusted weighted average common shares (denominator) 62.5 64.6 Amounts per share - diluted: Net (loss) income attributable to Cabot Corporation $ (0.11 ) $ 0.69 (1) Participating securities consist of shares of unvested time-based restricted stock units. Undistributed earnings are the earnings which remain after dividends declared during the period are assumed to be distributed to the common and participating shareholders. Undistributed earnings are allocated to common and participating shareholders on the same basis as dividend distributions. The calculation of undistributed earnings is as follows: Three Months Ended December 31, 2015 2014 (Dollars in millions) Calculation of undistributed earnings: Net (loss) income attributable to Cabot Corporation $ (7 ) $ 45 Less: Dividends declared on common stock 14 14 Less: Dividends declared on participating securities — — Undistributed (loss) earnings $ (21 ) $ 31 Allocation of undistributed (loss) earnings: Undistributed (loss) earnings allocated to common shareholders $ (21 ) $ 31 Undistributed (loss) earnings allocated to participating shareholders — — Undistributed (loss) earnings $ (21 ) $ 31 (2) Due to the Company’s net loss position, dividends on participating securities were not added back to the loss available to common shares for the three months ended December 31 , 2015 when calculating diluted EPS. ( 3 ) Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (4) below, and then reallocat ed to participating securities. ( 4 ) Represents incremental shares of common stock from the (i) assumed exercise of stock options issued under Cabot’s equity incentive plans; (ii) assumed issuance of shares to employees pursuant to the Company’s Deferred Compensation and Supplemental Retirement Plan; and (iii) assumed issuance of shares under outstanding performance-based restricted stock unit awards issued under Cabot’s equity incentive plans. The weighted average common shares outstanding for the three months ending December 31 , 2015 excludes 1,083,358 share s as those shares would be antidilutive due to the Company’s net loss position. For the three months ended December 31, 201 4, 325,500 incremental shares of common stock were not included in the calculation of diluted earnings per share because the inclusion of these shares would have been antidilutive.

Restructuring

Restructuring	3 Months Ended
	Dec. 31, 2015
Restructuring And Related Activities [Abstract]
Restructuring	J . Restructuring Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations as follows: Three Months Ended December 31, 2015 2014 (Dollars in millions) Cost of sales $ 37 $ 2 Selling and administrative expenses 6 5 Research and technical expenses 5 — Total $ 48 $ 7 Details of all restructuring activities and the related reserves during the three months ended December 31 , 2015 are as follows: Severance and Employee Benefits Environmental Remediation Asset Sales Asset Impairment and Accelerated Depreciation Other Total (Dollars in millions) Reserve at September 30, 2015 $ 5 $ 2 $ — $ — $ 2 $ 9 Charges (credit) 25 — (2 ) 23 2 48 Costs charged against assets / liabilities — — (5 ) (23 ) — (28 ) Cash (paid) received (11 ) — 7 — (3 ) (7 ) Reserve at December 31, 2015 $ 19 $ 2 $ — $ — $ 1 $ 22 2016 Plan On October 20, 2015, in response to challenging macroeconomic conditions, the Company announced its intention to restructure its operations subject to local consultation requirements and processes in certain locations. Cabot’s plan has resulted in a reduction of approximately 300 positions across the C ompany’s global locations. These actions are intended to result in a more competitive cost structure. The Company has recorded pre-tax charges of approximately $ 24 million in the first three months of fiscal 2016, and expects to record an additional $ 4 million through the rest of fiscal 2016 related to these actions. The charges recorded and anticipated are comprised of severance, employee benefits and other transition costs. Cumulative net cash outlays related to these actions are expected to be approximately $ 28 million, comprised of severance, employee benefits and other transition costs. Through December 31, 2015, the Company has made $ 11 million in cash payments related to this plan and expects to make $ 15 million in cash payments through the remainder of fiscal 2016 and $ 2 million thereafter. As of December 31, 2015, Cabot has $ 14 million of accrued severance costs in the Consolidated Balance Sheet related to this plan . Additionally, on November 11, 2015, Cabot announced that it had committed to closing its carbon black manufacturing facility in Merak, Indonesia. The decision to close this plant and to consolidate production in Asia using the Company’s Cilegon, Indonesia and other Asian and global carbon black production sites to meet regional demand was driven by the financial performance at the Merak facility in the past several years. Manufacturing operations ceased at the end of January 2016 and approximately 50 employees were affected . The Company has recorded pre-tax charges of approximately $ 2 4 million in the first three months of fiscal 2016 related to this closure , comprised of $ 2 2 million of asset impairments and accelerated depreciation and $ 2 million of severance and employee benefits. The asset impairment charges reflect the write-down of the long-lived assets group that is no longer in use to its fair value. Future anticipated site closure costs for the Merak facility , anticipated to be recorded through the remainder of fiscal 2016, are $ 6 million for site remediation and other miscellaneous costs. Net cash outlays related to this closure are expected to be approximately $ 8 million, substantially all of which is expected to be paid through the remainder of fiscal 2016. As of December 31, 2015, Cabot has $ 2 million of accrued severance costs in the Consolidated Balance Sheet related to the Merak facility closure . Details of the 2016 restructuring activities, including the Merak facility closure, during the three months ended December 31, 2015 are as follows: Severance and Employee Benefits Asset Impairment and Accelerated Depreciation Other Total (Dollars in millions) Reserve at September 30, 2015 $ — $ — $ — $ — Charges 25 22 1 48 Costs charged against assets / liabilities 1 (22 ) — (21 ) Cash paid (10 ) — (1 ) (11 ) Reserve at December 31, 2015 $ 16 $ — $ — $ 16 Business Service Center Transition I n January 2014, the Company announced its intention to open a new Europe, Middle East and Africa (“EMEA”) business service center in Riga, Latvia, and to close its Leuven, Belgium site, subject to the Belgian information and consultation process, which was successfully completed in June 2014. These actions were developed following an extensive evaluation of the Company’s business service capabilities in the EMEA region and a determination that the future EMEA business service center will enable the Company to provide the highest quality of service at the most competitive cost. The actions related to the transition of the business service center have been completed and have resulted in total charges of approximately $ 24 million , comprised of $ 16 million of severance charges and $ 8 million of other transition costs including training costs and redundant salaries. There were no charges related to this plan recorded in the first fiscal quarter of 2016 and $ 4 million was recorded related to this plan in the first fiscal quarter of 2015. Through December 31, 2015, the Company has made $ 2 0 million in cash payments related to this plan, comprised of $ 13 million of severance payments and $ 7 million of other transition related costs, and expects to make cash payments of approximately $ 1 million, comprised mainly of severance, in the remainder of fiscal 2016. The difference between the initial accrual and subsequent cash payments was due to changes in foreign exchange rates. As of December 31, 2015, Cabot has $ 1 million of accrued restructuring costs in the Consolidated Balance Sheet related to this closure, which is mainly comprised of accrued severance charges. Closure of Port Dickson, Malaysia Manufacturing Facility On April 26, 2013, the Company announced that the Board of its carbon black joint venture, Cabot Malaysia Sdn. Bhd. (“CMSB”), decided to cease production at its Port Dickson, Malaysia facility. The facility ceased production in June 2013. The Company holds a 50.1 percent equity share in CMSB. The decision, which affected approximately 90 carbon black employees, was driven by the facility’s manufacturing inefficiencies and raw materials costs. Through December 31, 2015, the Company recorded cumulative net pre-tax restructuring charges related to this plan of $ 19 million , comprised mainly of accelerated depreciation and asset write-offs of $ 16 million, severance charges of $ 2 million, site demolition, clearing and environmental remediation charges of $ 2 million, and other closure related charges of $ 1 million, partially offset by the gain from the sale of land of $ 2 million in fiscal 2016. CMSB’s net income or loss is attributable to Cabot Corporation and to the noncontrolling interest in the joint venture. The Company has recorded a net pre-tax gain of $ 1 million, and a net pre-tax charge of less than $ 1 million in the three months ended December 31, 2015 and 2014, respectively. The portion of the charges that are allocable to the noncontrolling interest in CMSB ( 49.9 %) are recorded within Net income attributable to noncontrolling interests, net of tax, in the Consolidated Statements of Operations. The majority of actions related to closure of the plant were completed in fiscal 2014. Cumulative net cash received related to this plan is $ 3 million, comprised of $ 7 million received from the sale of land, partially offset by approximately $ 2 million for severance, $ 1 million for site demolition, clearing and environmental remediation, and $ 1 million for other closure related charges. CMSB expects to make cash payments of less than $ 1 million during the remainder of fiscal 2016 mainly for site demolition, clearing and e nvironmental remediation costs. As of December 31, 2015, Cabot has less than $ 1 million of accrued restructuring costs in the Consolidated Balance Sheets related to this closure, which is mainly for accrued environmental and other charges. Other Activities The Company has recorded other pre-tax restructuring charges of approximately $ 1 million during each of the first quarters of fiscal 2016 and 2015. Fiscal 2016 charges are comprised mainly of accelerated depreciation and severance costs whereas fiscal 2015 charges are comprised of severance costs. Future charges related to these actions are anticipated to be less than $ 1 million in the remainder of fiscal 2016 and thereafter . As of December 31, 2015, Cabot has $ 3 million of accrued severance and other closure related costs in the Consolidated Balance Sheets related to these activities which is expected to be paid through early fiscal 2017. Previous Actions and Sites Pending Sale Beginning in fiscal 2009, the Company entered into several different restructuring plans which have been substantially completed, pending the sale of former manufacturing sites in Thane, India and Hong Kong. The Company has incurred total cumulative pre-tax charges of approximately $ 165 million related to these plans through December 31, 2015, comprised of $ 67 million for severance charges, $ 66 million for accelerated depreciation and asset impairments, $ 1 0 million for environmental, demolition and site clearing costs, and $ 2 3 million of other closure related charges, partially offset by gains on asset sales of $ 1 million. The Company anticipates that it will record a gain on the sale of land rights in Hong Kong of $ 8 million during fiscal 2016. Pre-tax restructuring expenses related to these plans were less than $ 1 million and $ 2 million during the first three months of fiscal 2016 and 2015, respectively. Since fiscal 2009, Cabot has made net cash payments of $ 87 million related to these plans and expects to receive approximately $ 9 million from the sale of land rights in Hong Kong during fiscal 2016 , partially offset by payments of approximately $ 2 million for environmental and other closure related costs . As of December 31, 2015, Cabot has $ 2 million of accrued environmental and other closure related costs in the Consolidated Balance Sheets related to these activities.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	3 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	K . Financial Instruments and Fair Value Measurements The FASB authoritative guidance on fair value measurements defines fair value, provides a framework for measuring fair value in generally accepted accounting principles, and requires certain disclosures about fair value measurements. The 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, or transfers into or out of Level 3, during the first three months of either fiscal 2016 or 2015 . At December 31, 2015 and September 30, 2015, the fair value of G uaranteed investment contr acts, included in Other assets o n the Consolidated Balance Sheets, was $ 11 million and $ 1 2 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, 2015 and September 30, 2015 , the fair values of cash and cash equivalents, accounts and notes receivable, accounts payable and accrued liabilities, and notes payable 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 $ 0.96 billion and $ 1.01 billion, respectively, as of December 31 , 2015 and $ 0.96 billion and $ 1.02 billion, respectively, as of September 30, 2015 . The fair values of Cabot’s fixed rate long-term debt and capital lease obligations 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, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivatives	L . Derivatives Interest Rate Risk Management Cabot’s objective is to maintain a certain fixed-to-variable interest rate mix on the Company’s debt obligations. Cabot may enter into interest rate swaps as a hedge of the underlying debt instruments to effectively change the characteristics of the interest rate without changing the debt instrument. As of both December 31, 2015 and September 30, 2015 , there were no derivatives held to manage interest rate risk. 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 its 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 a currency where the Company expects long-term, stable cash receipts. Additionally, the Company has foreign currency exposure arising from its net investments in foreign operations. Cabot, from time to time, enters 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, 2015 and September 30, 2015 to manage foreign currency risk. Notional Amount, net Description Borrowing December 31 , 2015 September 30, 2015 Hedge Designation Forward Foreign Currency Contracts (1) N/A USD 7 million USD 2 million No designation (1) Cabot’s forward foreign exchange contracts are denominated primarily in the British pound sterling, Czech koruna, and Indonesian rupiah . 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 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. 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 Accumulated other comprehensive (loss) income 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. 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 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. As of both December 31, 2015 and September 30, 2015 , the fair value of derivative instruments were immaterial and were presented in Prepaid expenses and other current assets and Accounts payable and accrued liabilities on the Consolidated Balance Sheets. The net after-tax amounts to be reclassified from AOCI to earnings within the next 12 months are expected to be immaterial.

Venezuela

Venezuela	3 Months Ended
	Dec. 31, 2015
Equity Method Investments And Joint Ventures [Abstract]
Venezuela	M . Venezuela Cabot owns 49 % of an operating carbon black affiliate in Venezuela, which is accounted for as an equity affiliate, through wholly-owned subsidiaries that carry the investment and receive its dividends. As of December 31 , 2015, these subsidiaries carried the operating affiliate investment of $ 13 million and held 1 7 million bolivars (less than $ 1 million) in cash. During each of the three month period s ended December 31, 2015 and 2014, the Company received dividends in the amount s of $ 2 million which were paid in U.S. dollars. A significant portion of the Company’s operating affiliate’s sales are exports denominated in U.S. dollars. The Venezuelan government mandates that a certain percentage of the dollars collected from these sales be converted into bolivars. The operating aff iliate and the Company’s wholly- owned subsidiari es used an exchange rate that was available to Cabot when converting these dollars into bolivars to remeasure their bolivar denominated monetary accounts. The exchange rate made available to us on December 31 , 2015 was 52 bolivars to the U.S. dollar . The operating entity has generally been profitable. The Company continues to closely monitor developments in Venezuela and their potential impact on the recoverability of its equity affiliate investment. Any future change in the exchange rate made available to the Company or opening of additional parallel markets could cause the Company to change the exchange rate it uses and result in gains or losses on the bolivar denominated assets held by its operating affiliate and wholly-owned subsidiaries.

Financial Information by Segmen

Financial Information by Segment	3 Months Ended
	Dec. 31, 2015
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”) 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. T he Company has four reportable segments : Reinforcement Materials, Performance Chemicals, Purification Solutions and Specialty Fluids. The Reinforcement Materials segment represents the rubber blacks and elastomer composites product lines. Performance Chemicals is comprised of two businesses: (i) our Specialty Carbons and Formulations business, which manufactures and sells specialty grades of carbon black, specialty compounds and inkjet colorants, and (ii) our Metal Oxides business, which manufactures and sells fumed silica, fumed a lumina and dispersions thereof and aerogel. The net sales from each of these businesses for the three months ended December 31, 2015 and 2014 are as follows: Three Months Ended December 31, 2015 2014 (Dollars in millions) Specialty Carbons and Formulations $ 140 $ 157 Metal Oxides 67 72 Total Performance Chemicals $ 207 $ 229 The Purification Solutions segment represents the Company’s activated carbon business and the Specialty Fluids segment includes cesium formate oil and gas drilling fluids and high-purity fine cesium chemicals product lines . Reportable segment operating profit (loss) before interest and taxes (“Segment EBIT”) is presented for each reportable segment in the financial information by reportable segment table below on the line entitled Income (loss) from continuing operations before taxes. Segment EBIT excludes certain items, meaning items management does not consider representative of segment results. In addition, Segment EBIT includes Equity in earnings (loss) 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, but excludes Interest expense, foreign currency transaction gains and losses, interest income, dividend income, unearned revenue, the effects of LIFO accounting for inventory, general unallocated expense and unallocated corporate costs. Financial information by reportable segment is as follows: Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids Segment Total Unallocated and Other (1) Consolidated Total (Dollars in millions) Three Months Ended December 31, 2015 Revenues from external customers (2) $ 288 $ 207 $ 66 $ 7 $ 568 $ 35 $ 603 Income (loss) from continuing operations before taxes (3) $ 26 $ 50 $ (5 ) $ — $ 71 $ (79 ) $ (8 ) Three Months Ended December 31, 2014 Revenues from external customers (2) $ 460 $ 229 $ 76 $ 16 $ 781 $ 31 $ 812 Income (loss) from continuing operations before taxes (3) $ 53 $ 39 $ (1 ) $ 6 $ 97 $ (46 ) $ 51 (1) Unallocated and Other includes certain items and eliminations necessary to reflect management’s reporting of operating segment results. These items are reflective of the segment reporting presented to the Chief Operating Decision Maker. (2) “ Unallocated and Other revenues from external customers ” reflects royalties, other operating revenues, external shipping and handling costs, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate and discounting charges for certain Notes receivable. Details are provided in the table below: Three Months Ended December 31, 2015 2014 (Dollars in millions) Royalties, other operating revenues, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate and discounting charges for certain Notes receivable. $ 9 $ 4 Shipping and handling fees 26 27 Total $ 35 $ 31 (3) Income (loss) from continuing operations before taxes that are categorized as Unallocated and Other includes: Three Months Ended December 31, 2015 2014 (Dollars in millions) Interest expense $ (13 ) $ (13 ) Total certain items, pre-tax (a) (58 ) (26 ) Equity in (earnings) loss of affiliated companies, net of tax (b) — (1 ) Unallocated corporate costs (c) (13 ) (12 ) General unallocated income (d) 5 6 Total $ (79 ) $ (46 ) (a) Certain items are items that management does not consider to be representative of operating segment results and they are, therefore, excluded from Segment EBIT. Certain items, pre-tax, for the three months ended December 3 1 , 2015 inc lude $ 4 8 million related to global restructuring activities, $ 8 million related to foreign currency loss on the devaluation of the Argentine peso , and $ 2 million related to legal and environmental matters and reserves . Certain items, pre-tax, for the three months ended December 31 , 201 4 include $ 7 million related to global restructuring activities, $ 1 million for acquisition and integration-related charges and $ 18 million related to an employee benefit plan settlement charge. (b) Equity in (earnings) loss of affiliated companies, net of tax , is included in Segment EBIT and is removed from Unallocated and other to reconcile to income (loss) from operations before taxes. (c) Unallocated corporate costs are not controlled by the segments and primarily benefit corporate interests. (d) General unallocated income consists of gains (losses) arising from foreign currency transactions, net of other foreign currency risk management activities, the impact of accounting for certain inventory on a LIFO basis, the profit or loss related to the corporate adjustment for unearned revenue, and the impact of including the full operating results of an equity affiliate in Purification Solutions Segment EBIT.

Significant Accounting Polici22

Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Revenue Recognition and Accounts Receivable	Revenue Recognition and Accounts Receivable Cabot recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable and collectability is reasonably assured. Cabot generally is able to ensure that products meet customer specifications prior to shipment. If the Company is unable to determine that the product has met the specified objective criteria prior to shipment or if title has not transferred because of sales terms, the revenue is considered “unearned” and is deferred until the revenue recognition criteria are met. Shipping and handling charges related to sales transactions are recorded as sales revenue when billed to customers or included in the sales price. Taxes collected on sales to customers are excluded from revenues. The following table shows the relative size of the revenue recognized in each of the Company’s reportable segments. Three Months Ended December 31, 2015 2014 Reinforcement Materials 51 % 59 % Performance Chemicals 36 % 29 % Purification Solutions 12 % 10 % Specialty Fluids 1 % 2 % Cabot derives the substantial majority of its revenues from the sale of products in Reinforcement Materials and Performance Chemicals. Revenue from these products is typically recognized when the product is shipped and title and risk of loss have passed to the customer. The Company offers certain of its customers cash discounts and volume rebates as sales incentives. The discounts and volume rebates are recorded as a reduction in sales at the time revenue is recognized and are estimated based on historical experience and contractual obligations. Cabot periodically reviews the assumptions underlying its estimates of discounts and volume rebates and adjusts its revenues accordingly. Revenue in Purification Solutions is typically recognized when the product is shipped and title and risk of loss have passed to the customer. For major activated carbon injection systems projects, revenue is recognized using the percentage-of-completion method . Revenue in Specialty Fluids arises primarily from the rental of cesium formate. This revenue is recognized throughout the rental period based on the contracted rental terms. Customers are also billed and revenue is recognized, typically at the end of the job, for cesium formate product that is not returned. The Company also generates revenues from cesium formate sold outside of a rental process and revenue is recognized upon delivery of the fluid . Cabot maintains allowances for doubtful accounts based on an assessment of the collectability of specific customer accounts, the aging of accounts receivable and other economic information on both a historical and prospective basis. Customer account balances are charged against the allowance when it is probable the receivable will not be recovered. There were no material changes in the allowance for any of the years presented. There is no material off-balance sheet credit exposure related to customer receivable balances .
Intangible Assets and Goodwill Impairment	Intangible Assets and Goodwill Impairment The Company records tangible and intangible assets acquired and liabilities assumed in business combinations under the acquisition method of accounting. Amounts paid for an acquisition are allocated to the assets acquired and liabilities assumed based on their fair values at the date of acquisition. 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 May 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. The reporting units with goodwill balances are Reinforcement Materials, Purification Solutions, and Fumed Metal Oxides. The separate businesses included within Performance Chemicals are considered separate reporting units. As such, the goodwill balance relative to Performance Chemicals is recorded in the Fumed Metal Oxides reporting unit. 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 under the two-step impairment test. 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, the Company performs an analysis of the fair value of all assets and liabilities of the reporting unit. If the implied fair value of the reporting unit’s goodwill is determined to be less than its carrying amount, an impairment is recognized for the difference. 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 companies 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. Should the fair value of any of the Company’s reporting units decline below its carrying amount because of reduced operating performance, market declines, changes in the discount rate, or other conditions, charges for impairment may be necessary. Based on the Company’s most recent annual goodwill impairment test performed as of May 31, 2015, the fair values of the Reinforcement Materials and Fumed Metal Oxides reporting units were substantially in excess of their carrying values. The fair value of the Purification Solutions reporting unit was less than its carrying amount and an impairment was recorded in the third fiscal quarter of 2015. Due to the impairment recorded as of June 30, 2015 , the fair value of the Purification Solutions reporting unit was insignificantly higher than its carrying value as of the last impairment date. No events occurred subsequent to the last impairment evaluation that would suggest that it is more likely than not that the carrying values of any of our reporting units exceeded their fair value. Nonetheless, the future growth in the Purification Solutions segment is highly dependent on achieving the expected volumes and margins in the activated carbon based mercury removal business. These volumes and margins are highly dependent on demand for mercury removal products and the Company’s successful realization of its anticipated share of volumes in this business. The expected demand for mercury removal products significantly depends on: (1) the implementation and enforcement of environmental laws and regulations, particularly those that would require U.S. based coal-fired electric utilities to reduce the quantity of air pollutants they release, including mercury, to comply with the Mercury and Air Toxics Standards (“MATS”) issued by the U.S. Environmental Protection Agency (“EPA”) and (2) other factors such as the anticipated usage of activated carbon in the coal-fired energy units. The MATS regulation has been subject to legal challenge and, in June 2015, the U.S. Supreme Court held that the EPA unreasonably failed to consider costs in determining whether it is necessary and appropriate to regulate hazardous air pollutants , including mercury, emitted by coal-fired utilities, and remanded the case back to the United States Co urt of Appeals for the District of Columbia Circuit Court for further proceedings. On December 15, 2015, the D.C. Circuit Court ruled to keep the MATS regulation in place while the EPA works to address the cost analysis required by the U.S. Supreme Court’s decision. EPA has indicated that it will complete this work by April 2016. 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. The Company recognized an impairment on intangible assets associated with the Purification Solutions business in the third fiscal quarter of 2015 and no events have been subsequently identified that would require an additional impairment evaluation.
Long-Lived Assets Impairment	Long-lived Assets Impairment The Company’s long-lived assets primarily include property, plant and equipment, intangible assets, long-term investments and assets held for rent. 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 market 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 separate identifiable cash flows, an impairment charge is recorded when the Company no longer intends to use the asset.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are recorded at cost. Depreciation of property, plant and equipment is calculated using the straight-line method over the estimated useful lives. The depreciable lives for buildings, machinery and equipment, and other fixed assets are twenty to twenty-five years, ten to twenty-five years, and three to 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 market. The cost of all carbon black inventories in the U.S. is determined using the last-in, first-out (“LIFO”) method. Had the Company used the first-in, first-out (“FIFO”) method instead of the LIFO method for such inventories, the value of those inventories would have been $ 28 million and $ 30 million higher as of December 31, 2015 and September 30, 2015, respectively. The cost of Specialty Fluids inventories, which are classified as assets held for rent, is determined using the average cost method. The cost of other U.S. and non-U.S. inventories is determined using the first-in, first-out (“FIFO”) method. Cabot 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. The Company is required to recognize as a component of other comprehensive income, 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 is adjusted as these amounts are later recognized in income as components of net periodic benefit cost.
Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive (Loss) Income Accumulated other comp rehensive (loss) income , which is included as a component of stockholders’ equity, includes unrealized gains or losses on available-for-sale marketable securities and derivative instruments , currency translation adjustments in foreign subsidiaries, translation adjustments on foreign equity securities and minimum pension liability adjustments.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued a new standard related to the “Revenue from Contracts with Customers” which amends the existing accounting standards for revenue recognition. The standard requires entities to recognize revenue when they transfer promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. This standard is applicable for fiscal years beginning after December 15, 201 7 and for interim periods within those years and early adoption is permitted for the fiscal years beginning after December 15, 2016 . The Company expects to adopt this standard on October 1, 201 8 . The Company is currently evaluating the impact the adoption of this standard may have on its consolidated financial statements . In April 2015, the FASB issued a new standard simplifying the presentation of debt issuance costs by requiring debt issuance costs to be presented as a reduction of the corresponding debt liability. This will make the presentation of debt issuance costs consistent with the presentation of debt discounts or premiums. This standard is applicable for fiscal years beginning after December 15, 2015 and for interim periods within those years and early adoption is permitted. The Company expects to adopt this standard on October 1, 2016. The adoption of this standard is not expected to materially impact the Company’s consolidated financial statements. In November 2015, the FASB issued a new standard that amends the existing accounting standard for Income Taxes and simplifies the presentation of deferred income taxes. This will require that deferred income tax assets and liabilities be classified as noncurrent on the balance sheet. This standard is applicable for fiscal years beginning after December 15, 2016 and for interim periods within those years and early adoption is permitted . The Company is evaluating this standard and the timing of its adoption . The adoption of this standard is not expected to materially impact the Company’s consolidated financial statements.

Significant Accounting Polici23

Significant Accounting Policies (Tables)	3 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Segment Reporting Revenue Percentage	The following table shows the relative size of the revenue recognized in each of the Company’s reportable segments. Three Months Ended December 31, 2015 2014 Reinforcement Materials 51 % 59 % Performance Chemicals 36 % 29 % Purification Solutions 12 % 10 % Specialty Fluids 1 % 2 %

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	3 Months Ended
	Dec. 31, 2015
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, 2015 2014 2015 2014 Pension Benefits Postretirement Benefits U.S. Foreign U.S. Foreign U.S. Foreign U.S. Foreign (Dollars in millions) Service cost $ — $ 2 $ — $ 2 $ — $ — $ — $ — Interest cost 1 2 2 3 — — — — Expected return on plan assets (3 ) (3 ) (3 ) (4 ) — — — — Amortization of prior service credit — — — — (1) — (1 ) — Amortization of actuarial loss — 1 — 1 — — — — Settlement and curtailment cost (credit) — — — 18 (1 ) — — — Net periodic (credit) benefit cost $ (2 ) $ 2 $ (1 ) $ 20 $ (2 ) $ — $ (1 ) $ —

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Dec. 31, 2015
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 , 2015 are as follows: Reinforcement Materials Performance Chemicals Purification Solutions Total (Dollars in millions) Balance at September 30, 2015 $ 55 $ 9 $ 90 $ 154 Foreign currency impact (1 ) — — (1 ) Balance at December 31, 2015 $ 54 $ 9 $ 90 $ 153
Schedule of Intangible Assets	The following table provides information regarding the Company’s intangible assets: December 31, 2015 September 30, 2015 Gross Carrying Value Accumulated Amortization Net Intangible Assets Gross Carrying Value Accumulated Amortization Net Intangible Assets (Dollars in millions) Intangible assets with finite lives Developed technologies $ 48 $ (2 ) $ 46 $ 48 $ (1 ) $ 47 Trademarks 15 — 15 16 — 16 Customer relationships 95 (7 ) 88 96 (6 ) 90 Total intangible assets $ 158 $ (9 ) $ 149 $ 160 $ (7 ) $ 153

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Schedule of Activity in Noncontrolling Interests	Noncontrolling interest The following table illustrates the noncontrolling interest activity for the periods presented: 2015 2014 (Dollars in millions) Balance at September 30 $ 104 $ 122 Net income attributable to noncontrolling interests 4 4 Noncontrolling interest foreign currency translation adjustment (3 ) (2 ) Noncontrolling interest dividends (9 ) — Balance at December 31 $ 96 $ 124 The dividends declared during the three months ended December 31, 2015 were not paid during the period.

Accumulated Other Comprehensi27

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Changes in Each Component of AOCI, Net of Tax	Changes in each component of AOCI, net of tax, are as follows: Currency Translation Adjustment Unrealized Gains on Investments Pension and Other Postretirement Benefit Liability Adjustments Total (Dollars in millions) Balance at September 30, 2015, attributable to Cabot Corporation $ (239 ) $ 2 $ (62 ) $ (299 ) Other comprehensive loss before reclassifications (47 ) — — (47 ) Amounts reclassified from accumulated other comprehensive (loss) income — — (1 ) (1 ) Net other comprehensive items (286 ) 2 (63 ) (347 ) Less: Noncontrolling interest (3 ) — — (3 ) Balance at December 31, 2015, attributable to Cabot Corporation $ (283 ) $ 2 $ (63 ) $ (344 )
Amounts Reclassified Out of AOCI	The amounts reclassified out of AOCI and into the Consolidated Statement s of Operations in the three months ended December 3 1 , 2015 and 2014 are as follows: Three Months Ended Affected Line Item in the Consolidated December 31, Statements of Operations 2015 2014 (Dollars in millions) Pension and other postretirement benefit liability adjustment Amortization of actuarial losses Net Periodic Benefit Cost - see Note C for details $ 1 $ 1 Amortization of prior service cost Net Periodic Benefit Cost - see Note C for details (1 ) (1 ) Settlement and curtailment (credit) cost Net Periodic Benefit Cost - see Note C for details (1 ) 27 Total before tax (1 ) 27 Tax impact Benefit for income taxes — (6 ) Total after tax $ (1 ) $ 21

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Dec. 31, 2015
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 those commitments, the amounts included in the table below are based on market prices at December 31 , 2015. Payments Due by Fiscal Year Remainder of Fiscal 2016 2017 2018 2019 2020 Thereafter Total (Dollars in millions) Reinforcement Materials $ 144 $ 136 $ 135 $ 132 $ 96 $ 1,702 $ 2,345 Performance Chemicals 44 50 37 32 29 155 347 Purification Solutions 10 7 1 — — — 18 Total $ 198 $ 193 $ 173 $ 164 $ 125 $ 1,857 $ 2,710

Income Tax (Tables)

Income Tax (Tables)	3 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Effective Tax Rate	Effective Tax Rate Three Months Ended December 31, 2015 2014 (Dollars in millions) (Benefit) Provision for income taxes $ (5 ) $ 3 Effective tax rate 74 % 5 %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Components of Basic and Diluted Earnings Per Common Share	The following tables summarize the components of the basic and diluted earnings per common share computations: Three Months Ended December 31, 2015 2014 (Dollars and shares in millions, except per share amounts) Basic EPS: Net (loss) income attributable to Cabot Corporation $ (7 ) $ 45 Less: Dividends and dividend equivalents to participating securities — — Less: Undistributed earnings allocated to participating securities (1) — — (Loss) earnings allocated to common shareholders (numerator) $ (7 ) $ 45 Weighted average common shares and participating securities outstanding 62.9 64.6 Less: Participating securities (1) 0.4 0.5 Adjusted weighted average common shares (denominator) 62.5 64.1 Amounts per share - basic: Net (loss) income attributable to Cabot Corporation $ (0.11 ) $ 0.70 Diluted EPS (2) : (Loss) earnings allocated to common shareholders $ (7 ) $ 45 Plus: (Loss) earnings allocated to participating securities — — Less: Adjusted earnings allocated to participating securities (3) — — (Loss) earnings allocated to common shareholders (numerator) $ (7 ) $ 45 Adjusted weighted average common shares outstanding 62.5 64.1 Effect of dilutive securities: Common shares issuable (4) — 0.5 Adjusted weighted average common shares (denominator) 62.5 64.6 Amounts per share - diluted: Net (loss) income attributable to Cabot Corporation $ (0.11 ) $ 0.69 (1) Participating securities consist of shares of unvested time-based restricted stock units.
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, 2015 2014 (Dollars in millions) Calculation of undistributed earnings: Net (loss) income attributable to Cabot Corporation $ (7 ) $ 45 Less: Dividends declared on common stock 14 14 Less: Dividends declared on participating securities — — Undistributed (loss) earnings $ (21 ) $ 31 Allocation of undistributed (loss) earnings: Undistributed (loss) earnings allocated to common shareholders $ (21 ) $ 31 Undistributed (loss) earnings allocated to participating shareholders — — Undistributed (loss) earnings $ (21 ) $ 31 (2) Due to the Company’s net loss position, dividends on participating securities were not added back to the loss available to common shares for the three months ended December 31 , 2015 when calculating diluted EPS. ( 3 ) Undistributed earnings are adjusted for the assumed distribution of dividends to the dilutive securities, which are described in (4) below, and then reallocat ed to participating securities. ( 4 ) Represents incremental shares of common stock from the (i) assumed exercise of stock options issued under Cabot’s equity incentive plans; (ii) assumed issuance of shares to employees pursuant to the Company’s Deferred Compensation and Supplemental Retirement Plan; and (iii) assumed issuance of shares under outstanding performance-based restricted stock unit awards issued under Cabot’s equity incentive plans. The weighted average common shares outstanding for the three months ending December 31 , 2015 excludes 1,083,358 share s as those shares would be antidilutive due to the Company’s net loss position. For the three months ended December 31, 201 4, 325,500 incremental shares of common stock were not included in 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, 2015
Recorded Restructuring Activities	Cabot’s restructuring activities were recorded in the Consolidated Statements of Operations as follows: Three Months Ended December 31, 2015 2014 (Dollars in millions) Cost of sales $ 37 $ 2 Selling and administrative expenses 6 5 Research and technical expenses 5 — Total $ 48 $ 7
Restructuring Activities and Related Reserves	Details of all restructuring activities and the related reserves during the three months ended December 31 , 2015 are as follows: Severance and Employee Benefits Environmental Remediation Asset Sales Asset Impairment and Accelerated Depreciation Other Total (Dollars in millions) Reserve at September 30, 2015 $ 5 $ 2 $ — $ — $ 2 $ 9 Charges (credit) 25 — (2 ) 23 2 48 Costs charged against assets / liabilities — — (5 ) (23 ) — (28 ) Cash (paid) received (11 ) — 7 — (3 ) (7 ) Reserve at December 31, 2015 $ 19 $ 2 $ — $ — $ 1 $ 22
2016 Plan [Member]
Restructuring Activities and Related Reserves	Details of the 2016 restructuring activities, including the Merak facility closure, during the three months ended December 31, 2015 are as follows: Severance and Employee Benefits Asset Impairment and Accelerated Depreciation Other Total (Dollars in millions) Reserve at September 30, 2015 $ — $ — $ — $ — Charges 25 22 1 48 Costs charged against assets / liabilities 1 (22 ) — (21 ) Cash paid (10 ) — (1 ) (11 ) Reserve at December 31, 2015 $ 16 $ — $ — $ 16

Derivatives (Tables)

Derivatives (Tables)	3 Months Ended
	Dec. 31, 2015
Forward Foreign Currency Contracts [Member]
Details of Derivatives Held to Manage Foreign Currency Risk	The following table provides details of the derivatives held as of December 31, 2015 and September 30, 2015 to manage foreign currency risk. Notional Amount, net Description Borrowing December 31 , 2015 September 30, 2015 Hedge Designation Forward Foreign Currency Contracts (1) N/A USD 7 million USD 2 million No designation (1) Cabot’s forward foreign exchange contracts are denominated primarily in the British pound sterling, Czech koruna, and Indonesian rupiah .

Financial Information by Segm33

Financial Information by Segment (Tables)	3 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Schedule of Performance Segment	The net sales from each of these businesses for the three months ended December 31, 2015 and 2014 are as follows: Three Months Ended December 31, 2015 2014 (Dollars in millions) Specialty Carbons and Formulations $ 140 $ 157 Metal Oxides 67 72 Total Performance Chemicals $ 207 $ 229
Financial Information by Reportable Segment	Financial information by reportable segment is as follows: Reinforcement Materials Performance Chemicals Purification Solutions Specialty Fluids Segment Total Unallocated and Other (1) Consolidated Total (Dollars in millions) Three Months Ended December 31, 2015 Revenues from external customers (2) $ 288 $ 207 $ 66 $ 7 $ 568 $ 35 $ 603 Income (loss) from continuing operations before taxes (3) $ 26 $ 50 $ (5 ) $ — $ 71 $ (79 ) $ (8 ) Three Months Ended December 31, 2014 Revenues from external customers (2) $ 460 $ 229 $ 76 $ 16 $ 781 $ 31 $ 812 Income (loss) from continuing operations before taxes (3) $ 53 $ 39 $ (1 ) $ 6 $ 97 $ (46 ) $ 51 (1) Unallocated and Other includes certain items and eliminations necessary to reflect management’s reporting of operating segment results. These items are reflective of the segment reporting presented to the Chief Operating Decision Maker. (2) “ Unallocated and Other revenues from external customers ” reflects royalties, other operating revenues, external shipping and handling costs, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate and discounting charges for certain Notes receivable. Details are provided in the table below: Three Months Ended December 31, 2015 2014 (Dollars in millions) Royalties, other operating revenues, the impact of unearned revenue, the removal of 100 % of the sales of an equity method affiliate and discounting charges for certain Notes receivable. $ 9 $ 4 Shipping and handling fees 26 27 Total $ 35 $ 31 (3) Income (loss) from continuing operations before taxes that are categorized as Unallocated and Other includes: Three Months Ended December 31, 2015 2014 (Dollars in millions) Interest expense $ (13 ) $ (13 ) Total certain items, pre-tax (a) (58 ) (26 ) Equity in (earnings) loss of affiliated companies, net of tax (b) — (1 ) Unallocated corporate costs (c) (13 ) (12 ) General unallocated income (d) 5 6 Total $ (79 ) $ (46 ) (a) Certain items are items that management does not consider to be representative of operating segment results and they are, therefore, excluded from Segment EBIT. Certain items, pre-tax, for the three months ended December 3 1 , 2015 inc lude $ 4 8 million related to global restructuring activities, $ 8 million related to foreign currency loss on the devaluation of the Argentine peso , and $ 2 million related to legal and environmental matters and reserves . Certain items, pre-tax, for the three months ended December 31 , 201 4 include $ 7 million related to global restructuring activities, $ 1 million for acquisition and integration-related charges and $ 18 million related to an employee benefit plan settlement charge. (b) Equity in (earnings) loss of affiliated companies, net of tax , is included in Segment EBIT and is removed from Unallocated and other to reconcile to income (loss) from operations before taxes. (c) Unallocated corporate costs are not controlled by the segments and primarily benefit corporate interests. (d) General unallocated income consists of gains (losses) arising from foreign currency transactions, net of other foreign currency risk management activities, the impact of accounting for certain inventory on a LIFO basis, the profit or loss related to the corporate adjustment for unearned revenue, and the impact of including the full operating results of an equity affiliate in Purification Solutions Segment EBIT.

Significant Accounting Polici34

Significant Accounting Policies - Segment Reporting Revenue Percentage (Detail) - Sales Revenue, Segment [Member] - Revenue from Rights Concentration Risk [Member]	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	51.00%	59.00%
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	36.00%	29.00%
Purification Solutions [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	12.00%	10.00%
Specialty Fluids [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	1.00%	2.00%

Significant Accounting Polici35

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Sep. 30, 2015
Significant Accounting Policies [Line Items]
Value of inventories under FIFO method	$ 28	$ 30
Buildings [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	20 years
Buildings [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	25 years
Machinery and Equipment [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	10 years
Machinery and Equipment [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	25 years
Other Fixed Assets [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	3 years
Other Fixed Assets [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life of property, plant and equipment	25 years

Employee Benefit Plans - Net Pe

Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
U.S. Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 2
Expected return on plan assets	(3)	(3)
Net periodic (credit) benefit cost	(2)	(1)
Foreign Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2
Interest cost	2	3
Expected return on plan assets	(3)	(4)
Amortization of actuarial loss	1	1
Settlement and curtailment cost (credit)		18
Net periodic (credit) benefit cost	2	20
U. S. Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service credit	(1)	(1)
Settlement and curtailment cost (credit)	(1)
Net periodic (credit) benefit cost	$ (2)	$ (1)

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Compensation And Retirement Disclosure [Abstract]
Settlement costs		$ 18
Pre-tax charge from AOCI	$ 27
Settlement charges on pension liability	11
Settlement charges on employer contributions	$ 2

Goodwill and Intangible Asset38

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Goodwill And Intangible Assets [Line Items]
Goodwill	$ 153		$ 154
Amortization expense estimated for year one	9
Amortization expense estimated for year two	9
Amortization expense estimated for year three	9
Amortization expense estimated for year four	9
Amortization expense estimated for year five	9
Cost of Sales and Selling and Administrative Expenses [Member]
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ 2	$ 4
Minimum [Member]
Goodwill And Intangible Assets [Line Items]
Useful life of intangible assets	14 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

Goodwill and Intangible Asset39

Goodwill and Intangible Assets - Schedule of Goodwill Balances (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2015USD ($)
Goodwill And Intangible Assets [Line Items]
Beginning balance	$ 154
Foreign currency impact	(1)
Ending balance	153
Reinforcement Materials [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	55
Foreign currency impact	(1)
Ending balance	54
Performance Chemicals [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	9
Ending balance	9
Purification Solutions [Member]
Goodwill And Intangible Assets [Line Items]
Beginning balance	90
Ending balance	$ 90

Goodwill and Intangible Asset40

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	$ 158	$ 160
Accumulated Amortization	(9)	(7)
Net Intangible Assets, finite lives	149	153
Developed Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	48	48
Accumulated Amortization	(2)	(1)
Net Intangible Assets, finite lives	46	47
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	15	16
Net Intangible Assets, finite lives	15	16
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value, finite lives	95	96
Accumulated Amortization	(7)	(6)
Net Intangible Assets, finite lives	$ 88	$ 90

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2015	Sep. 30, 2007
Class Of Stock [Line Items]
Repurchase authorization, shares			5,000,000	10,000,000
Cash dividends paid to common stockholders	$ 14,000,000	$ 14,000,000
Cash dividend paid per share	$ 0.22	$ 0.22
Dividend declared but not paid	$ 0
2007 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased	925,700
January 2015 Share Repurchase Authorization [Member]
Class Of Stock [Line Items]
Common stock shares repurchased	1,594,300
Shares remaining available for repurchase under the current authorization	3,405,700

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Activity in Noncontrolling Interests (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Balance at September 30	$ 104	$ 122
Net income attributable to noncontrolling interests	4	4
Noncontrolling interest foreign currency translation adjustment	(3)	(2)
Noncontrolling interest dividends	(9)
Balance at December 31	$ 96	$ 124

Accumulated Other Comprehensi43

Accumulated Other Comprehensive Loss - Changes in Each Component of AOCI, Net of Tax (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Balance attributable to Cabot Corporation	$ (299)
Other comprehensive loss before reclassifications	(47)
Amounts reclassified from accumulated other comprehensive (loss) income	(1)	$ 21
Net other comprehensive items	(347)
Less: Noncontrolling interest	(3)
Balance attributable to Cabot Corporation	(344)
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance attributable to Cabot Corporation	(239)
Other comprehensive loss before reclassifications	(47)
Net other comprehensive items	(286)
Less: Noncontrolling interest	(3)
Balance attributable to Cabot Corporation	(283)
Unrealized Gains on Investments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance attributable to Cabot Corporation	2
Net other comprehensive items	2
Balance attributable to Cabot Corporation	2
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance attributable to Cabot Corporation	(62)
Amounts reclassified from accumulated other comprehensive (loss) income	(1)
Net other comprehensive items	(63)
Balance attributable to Cabot Corporation	$ (63)

Accumulated Other Comprehensi44

Accumulated Other Comprehensive Loss - Amounts Reclassified Out of AOCI (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (1)	$ 27
Tax impact		(6)
Total after tax	(1)	21
Pension and Other Postretirement Benefit Liability Adjustments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial losses	1	1
Amortization of prior service cost	(1)	(1)
Settlement and curtailment (credit) cost	1	$ (27)
Total after tax	$ (1)

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Components of Purchase Commitments (Detail) $ in Millions	Dec. 31, 2015USD ($)
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2016	$ 198
Payments Due by Fiscal Year 2017	193
Payments Due by Fiscal Year 2018	173
Payments Due by Fiscal Year 2019	164
Payments Due by Fiscal Year 2020	125
Payments Due Thereafter	1,857
Payments Due, Total	2,710
Reinforcement Materials [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2016	144
Payments Due by Fiscal Year 2017	136
Payments Due by Fiscal Year 2018	135
Payments Due by Fiscal Year 2019	132
Payments Due by Fiscal Year 2020	96
Payments Due Thereafter	1,702
Payments Due, Total	2,345
Performance Chemicals [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2016	44
Payments Due by Fiscal Year 2017	50
Payments Due by Fiscal Year 2018	37
Payments Due by Fiscal Year 2019	32
Payments Due by Fiscal Year 2020	29
Payments Due Thereafter	155
Payments Due, Total	347
Purification Solutions [Member]
Long-term Purchase Commitment [Line Items]
Payments Due by Remainder of Fiscal Year 2016	10
Payments Due by Fiscal Year 2017	7
Payments Due by Fiscal Year 2018	1
Payments Due, Total	$ 18

Commitments and Contingencies46

Commitments and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2015USD ($)claimants	Dec. 31, 2014USD ($)	Sep. 30, 2015USD ($)claimants
Respirator Liabilities [Member]
Loss Contingencies [Line Items]
Number of claimants | claimants	37,000		38,000
Respirator reserve	$ 10		$ 11
Cash payments for respirator reserves	1	$ 1
Environmental Matters [Member]
Loss Contingencies [Line Items]
Reserved for environmental matters	15		$ 16
Cash payments for environmental reserves	$ 1	$ 1

Income Tax - Effective Tax Rate

Income Tax - Effective Tax Rate (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
(Benefit) Provision for income taxes	$ (5)	$ 3
Effective tax rate	74.00%	5.00%

Income Tax - Additional Informa

Income Tax - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
(Benefit) Provision for income taxes	$ (5)	$ 3
Effective tax rate	74.00%	5.00%
Net discrete tax (benefits) charges related to tax settlements	$ (6)	$ (13)
Uncertain tax positions from expirations of statute of limitations	$ 2
Earliest Tax Year [Member] | Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,012
Earliest Tax Year [Member] | State Tax Authorities [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,005
Earliest Tax Year [Member] | Non-U.S. Jurisdictions [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,004
Latest Tax Year [Member] | Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,015
Latest Tax Year [Member] | State Tax Authorities [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,015
Latest Tax Year [Member] | Non-U.S. Jurisdictions [Member]
Income Taxes [Line Items]
Tax years remain subject to examination	2,015

Earnings Per Share - Components

Earnings Per Share - Components of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Basic EPS:
Net (loss) income attributable to Cabot Corporation	$ (7)	$ 45
(Loss) earnings allocated to common shareholders (numerator)	$ (7)	$ 45
Weighted average common shares and participating securities outstanding	62.9	64.6
Less: Participating securities	0.4	0.5
Adjusted weighted average common shares (denominator)	62.5	64.1
Net (loss) income attributable to Cabot Corporation	$ (0.11)	$ 0.70
Diluted EPS:
(Loss) earnings allocated to common shareholders	$ (7)	$ 45
(Loss) earnings allocated to common shareholders (numerator)	$ (7)	$ 45
Adjusted weighted average common shares (denominator)	62.5	64.1
Common shares issuable		0.5
Adjusted weighted average common shares (denominator)	62.5	64.6
Net (loss) income attributable to Cabot Corporation	$ (0.11)	$ 0.69

Earnings Per Share - Calculatio

Earnings Per Share - Calculation of Undistributed Earnings (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net (loss) income attributable to Cabot Corporation	$ (7)	$ 45
Less: Dividends declared on common stock	14	14
Undistributed (loss) earnings	(21)	31
Undistributed (loss) earnings allocated to common shareholders	$ (21)	$ 31

Earnings Per Share - Calculat51

Earnings Per Share - Calculation of Undistributed Earnings (Parenthetical) (Detail) - shares	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share	1,083,358	325,500

Restructuring - Recorded Restru

Restructuring - Recorded Restructuring Activities (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 48	$ 7
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	37	2
Selling and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	6	$ 5
Research and Technical Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring reserve, period expense	$ 5

Restructuring - Restructuring A

Restructuring - Restructuring Activities and Related Reserves (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2015USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 9
Charges (credit)	48
Costs charged against assets / liabilities	(28)
Cash (paid) received	(7)
Reserve balance	22
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	5
Charges (credit)	25
Cash (paid) received	(11)
Reserve balance	19
Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2
Reserve balance	2
Asset Sales [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	(2)
Costs charged against assets / liabilities	(5)
Cash (paid) received	7
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges (credit)	23
Costs charged against assets / liabilities	(23)
Other [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2
Charges (credit)	2
Cash (paid) received	(3)
Reserve balance	$ 1

Restructuring - Additional Info

Restructuring - Additional Information (Detail)	Nov. 11, 2015Employees	Oct. 20, 2015Position	Apr. 26, 2013Employees	Dec. 31, 2015USD ($)	Jan. 31, 2014USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						$ 48,000,000	$ 7,000,000
Restructuring costs in accrued expenses				$ 22,000,000		22,000,000				$ 22,000,000	$ 9,000,000
Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						1,000,000	1,000,000
Severance Costs [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges				3,000,000		3,000,000				3,000,000
Scenario Forecast [Member] | Maximum [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Additional restructuring charges after current fiscal								$ 1,000,000
Operational Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Number of positions eliminated | Position		300
Pre-tax charge to earnings						24,000,000
Expected cumulative net cash outlays related to plan				28,000,000		28,000,000				28,000,000
Cash payments						11,000,000
Restructuring cash payments through the reminder of fiscal 2016						15,000,000
Restructuring cash payments, thereafter						2,000,000
Operational Restructuring [Member] | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges				14,000,000		14,000,000				14,000,000
Operational Restructuring [Member] | Scenario Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Additional restructuring charges after current fiscal								4,000,000
Closure of Carbon Black Facility [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						24,000,000
Affected employees | Employees	50
Closure of Carbon Black Facility [Member] | Severance Costs [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges				2,000,000		2,000,000				2,000,000
Closure of Carbon Black Facility [Member] | Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						22,000,000
Closure of Carbon Black Facility [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						2,000,000
Closure of Carbon Black Facility [Member] | Scenario Forecast [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash outlays related to plan								8,000,000	$ 8,000,000
Site demolition and other miscellaneous costs									6,000,000
Shared Service Center Transition [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings					$ 24,000,000	0	4,000,000
Cash payments						20,000,000
Severance charges					16,000,000	13,000,000
Other charges					$ 8,000,000	7,000,000
Expected restructuring charges				1,000,000		1,000,000				1,000,000
Restructuring costs in accrued expenses				1,000,000		1,000,000				1,000,000
Closure of Port Dickson [Member]
Restructuring Cost And Reserve [Line Items]
Affected employees | Employees			90
Severance charges						2,000,000
Other charges						1,000,000
Expected restructuring charges				19,000,000		19,000,000				19,000,000
Net pre-tax gain						1,000,000
Accelerated depreciation and asset write-offs						16,000,000
Site demolition, clearing and environmental remediation costs						2,000,000
Expected cumulative net cash received to this plan				3,000,000		3,000,000				3,000,000
Closure of Port Dickson [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected restructuring charges							1,000,000
Restructuring costs in accrued expenses				$ 1,000,000		$ 1,000,000				$ 1,000,000
Closure of Port Dickson [Member] | Cabot [Member]
Restructuring Cost And Reserve [Line Items]
Equity share in CMSB			50.10%
Closure of Port Dickson [Member] | CMSB [Member]
Restructuring Cost And Reserve [Line Items]
Portion of the charges that are allocable to the noncontrolling interest				49.90%		49.90%				49.90%
Closure of Port Dickson [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan				$ 2,000,000		$ 2,000,000				$ 2,000,000
Closure of Port Dickson [Member] | Asset Sales [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan				7,000,000		7,000,000				7,000,000
Closure of Port Dickson [Member] | Environmental Remediation [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan				1,000,000		1,000,000				1,000,000
Closure of Port Dickson [Member] | Facility Closure Costs [Member]
Restructuring Cost And Reserve [Line Items]
Expected cumulative net cash received to this plan				1,000,000		1,000,000				1,000,000
Closure of Port Dickson [Member] | Scenario Forecast [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Cash payments								$ 1,000,000
Closure of Port Dickson [Member] | Scenario Forecast [Member] | Land [Member]
Restructuring Cost And Reserve [Line Items]
Gain on sale of asset									2,000,000
Previous Actions and Sites Pending Sale [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings							$ 2,000,000
Cash payments										87,000,000
Severance charges				67,000,000
Other charges				23,000,000
Expected restructuring charges				165,000,000		165,000,000				165,000,000
Gain on sale of asset				1,000,000
Site demolition, clearing and environmental remediation costs				10,000,000
Restructuring accelerated depreciation and asset impairments				66,000,000
Previous Actions and Sites Pending Sale [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Pre-tax charge to earnings						1,000,000
Previous Actions and Sites Pending Sale [Member] | Severance Costs [Member] | Restructuring Activities Other [Member]
Restructuring Cost And Reserve [Line Items]
Accrued severance charges				$ 2,000,000		$ 2,000,000				$ 2,000,000
Previous Actions and Sites Pending Sale [Member] | Scenario Forecast [Member] | Land Rights [Member]
Restructuring Cost And Reserve [Line Items]
Gain on sale of asset									8,000,000
Expected cash received from sale of land rights									9,000,000
Previous Actions and Sites Pending Sale [Member] | Scenario Forecast [Member] | Environmental and Other Closure Related Costs [Member]
Restructuring Cost And Reserve [Line Items]
Cash payments									$ 2,000,000

Restructuring - Restructuring55

Restructuring - Restructuring Activities Including Merak Facility Closure (Detail) $ in Millions	3 Months Ended
	Dec. 31, 2015USD ($)
Restructuring Cost And Reserve [Line Items]
Reserve balance	$ 9
Charges	48
Cash paid	(7)
Reserve balance	22
Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	5
Charges	25
Cash paid	(11)
Reserve balance	19
Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges	23
Other [Member]
Restructuring Cost And Reserve [Line Items]
Reserve balance	2
Charges	2
Cash paid	(3)
Reserve balance	1
2016 Plan [Member]
Restructuring Cost And Reserve [Line Items]
Charges	48
Costs charged against assets / liabilities	(21)
Cash paid	(11)
Reserve balance	16
2016 Plan [Member] | Severance and Employee Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Charges	25
Costs charged against assets / liabilities	1
Cash paid	(10)
Reserve balance	16
2016 Plan [Member] | Asset Impairment and Accelerated Depreciation [Member]
Restructuring Cost And Reserve [Line Items]
Charges	22
Costs charged against assets / liabilities	(22)
2016 Plan [Member] | Other [Member]
Restructuring Cost And Reserve [Line Items]
Charges	1
Cash paid	$ (1)

Financial Instruments and Fai56

Financial Instruments and Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
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	1,010,000,000		$ 1,020,000,000
Fixed Rate Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of long-term debt	960,000,000		960,000,000
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		$ 12,000,000

Derivative - Additional Informa

Derivative - Additional Information (Detail) - USD ($)	Dec. 31, 2015	Sep. 30, 2015
Fair Value Hedging [Member] | Interest Rate Swap-Fixed to Variable [Member]
Derivative [Line Items]
Derivatives held to manage interest rate risk	$ 0	$ 0

Derivatives - Details of Deriva

Derivatives - Details of Derivatives Held to Manage Foreign Currency Risk (Detail) - USD ($)		Dec. 31, 2015	Sep. 30, 2015
Not Designated as Hedging Instrument [Member] | Forward Foreign Currency Contracts [Member]
Derivative [Line Items]
Notional amount, net of forward foreign currency contract no designation hedge derivatives	[1]	$ 7,000,000	$ 2,000,000
[1]	Cabot’s forward foreign exchange contracts are denominated primarily in the British pound sterling, Czech koruna, and Indonesian rupiah.

Venezuela - Additional Informat

Venezuela - Additional Information (Detail) VEF in Millions	3 Months Ended
	Dec. 31, 2015USD ($)VEB / $	Dec. 31, 2014USD ($)	Dec. 31, 2015VEFVEB / $
Nature Of Operations [Line Items]
Operating affiliate investment	$ 13,000,000
Due from affiliates, dividends cash | VEF			VEF 17
Conversion of Bolivars to USD | VEB / $	52		52
Subsidiaries
Nature Of Operations [Line Items]
Cash dividends received from subsidiary	$ 2,000,000	$ 2,000,000
Maximum [Member]
Nature Of Operations [Line Items]
Due from affiliates, dividends cash	$ 1,000,000
Venezuela [Member] | Carbon Black Affiliate [Member]
Nature Of Operations [Line Items]
Equity method investment, ownership percentage	49.00%		49.00%

Financial Information by Segm60

Financial Information by Segment - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2015SegmentBusiness_Unit
Segment Reporting Information [Line Items]
Number of business reportable segments | Segment	4
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Number of business activity | Business_Unit	2

Financial Information by Segm61

Financial Information by Segment - Schedule of Performance Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 603	$ 812
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	568	781
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	207	229
Performance Chemicals [Member] | Specialty Carbons and Formulations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	140	157
Performance Chemicals [Member] | Metal Oxides [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	$ 67	$ 72

Financial Information by Segm62

Financial Information by Segment - Financial Information by Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues from external customers	$ 603	$ 812
Income (loss) from continuing operations before taxes	(8)	51
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	568	781
Income (loss) from continuing operations before taxes	71	97
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	35	31
Income (loss) from continuing operations before taxes	(79)	(46)
Reinforcement Materials [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	288	460
Income (loss) from continuing operations before taxes	26	53
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	207	229
Income (loss) from continuing operations before taxes	50	39
Purification Solutions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	66	76
Income (loss) from continuing operations before taxes	(5)	(1)
Specialty Fluids [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	$ 7	16
Income (loss) from continuing operations before taxes		$ 6

Financial Information by Segm63

Financial Information by Segment - Financial Information by Reportable Segment (Parenthetical) (Detail)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%

Financial Information by Segm64

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 603	$ 812
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Net sales	35	31
Unallocated and Other [Member] | Royalties, Other Operating Revenues, 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]
Net sales	9	4
Unallocated and Other [Member] | Shipping and Handling Costs [Member]
Segment Reporting Information [Line Items]
Net sales	$ 26	$ 27

Financial Information by Segm65

Financial Information by Segment - Sales of Equity Method Affiliate and Discounting Charges for Certain Notes Receivable (Parenthetical) (Detail)	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Percentage of sale of an equity method affiliate	100.00%	100.00%

Financial Information by Segm66

Financial Information by Segment - Schedule of Income (Loss) from Continuing Operations before Taxes for Unallocated and Other (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Interest expense	$ (13)	$ (13)
Unallocated and Other [Member]
Segment Reporting Information [Line Items]
Interest expense	(13)	(13)
Total certain items, pre-tax	(58)	(26)
Equity in (earnings) loss of affiliated companies, net of tax		(1)
Unallocated corporate costs	(13)	(12)
General unallocated income	5	6
Income from continuing operations before income taxes and equity in earnings of affiliated companies	$ (79)	$ (46)

Financial Information by Segm67

Financial Information by Segment - Schedule of Income (Loss) from Continuing Operations before Taxes for Unallocated and Other (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Restructuring reserve, period expense	$ 48	$ 7
Employee benefit plan settlement charge		18
Certain Item [Member]
Segment Reporting Information [Line Items]
Restructuring reserve, period expense	48	7
Charges for environmental expense	2
Acquisition and integration related charges		1
Employee benefit plan settlement charge		$ 18
Certain Item [Member] | Devaluation of Argentine Peso [Member]
Segment Reporting Information [Line Items]
Foreign currency exchange rate, re measurement loss	$ 8