Commitments and Contingencies	9 Months Ended
Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	G. Commitments and Contingencies Contingencies Respirator Liabilities Cabot has exposure in connection with a safety respiratory products business that a subsidiary acquired from American Optical Corporation (“AO”) in an April 1990 asset purchase transaction. The subsidiary manufactured respirators under the AO brand and disposed of that business in July 1995. In connection with its acquisition of the business, the subsidiary agreed, in certain circumstances, to assume a portion of AO’s liabilities, including costs of legal fees together with amounts paid in settlements and judgments, allocable to AO respiratory products used prior to the 1990 purchase by the Cabot subsidiary. In exchange for the subsidiary’s assumption of certain of AO’s respirator liabilities, AO agreed to provide to the subsidiary the benefits of: (i) AO’s insurance coverage for the period prior to the 1990 acquisition and (ii) a former owner’s indemnity of AO holding it harmless from any liability allocable to AO respiratory products used prior to May 1982. As more fully described in the 2019 10-K, the respirator liabilities generally involve claims for personal injury, including asbestosis, silicosis and coal worker’s pneumoconiosis, allegedly resulting from the use of respirators that are alleged to have been negligently designed and/or labeled. Neither Cabot, nor its past or present subsidiaries, at any time manufactured asbestos or asbestos-containing products. At no time did this respiratory product line represent a significant portion of the respirator market. In addition to Cabot’s subsidiary, other parties are responsible for significant portions of the costs of these respirator liabilities (as defined in the 2019 10-K, the “Payor Group”). On February 28, 2020, Cabot, with certain members of the Payor Group, entered into a settlement agreement resolving a large group of claims, including claims alleging serious injury, brought by coal workers in Kentucky and West Virginia represented by common legal counsel. The Company’s share of this liability is $65.2 million, and during the second quarter of fiscal 2020, Cabot recorded a charge of $50 million for this settlement, which was included in Selling and administrative expenses in the Consolidated Statements of Operations. The Company paid $32.6 million of the settlement during the third quarter of fiscal 2020 and the remaining $32.6 million, which is included in Accounts payable and accrued liabilities on the Consolidated Balance Sheets as of June 30, 2020, will be paid in the first quarter of fiscal 2021. In addition to the February 2020 settlement, Cabot has a reserve to cover its expected share of liabilities for existing and future respirator liability claims, which is included in Other liabilities and Accounts payable and accrued liabilities on the Consolidated Balance Sheets. The Company expects these liabilities to be incurred over a number of years. The reserve was $21 million and $35 million as of June 30, 2020 and September 30, 2019, respectively. The Company’s current estimate of the cost of its share of existing and future respirator liability claims is based on facts and circumstances existing at this time, including the nature of the remaining claims. Because reserves are limited to amounts that are probable and estimable as of a relevant measurement date, and there is inherent difficulty in projecting the impact of potential developments on Cabot’s share of liability for these existing and future claims, the actual amount of liabilities related to these claims could be different from Cabot’s reserve. Developments that could affect the Company’s estimate include, but are not limited to, (i) significant changes in the number of future claims, (ii) changes in the rate of dismissals without payment of pending claims, (iii) significant changes in the average cost of resolving claims, including potential settlements of groups of claims, (iv) significant changes in the legal costs of defending these claims, (v) changes in the nature of claims received, (vi) trial and appellate outcomes, (vii) changes in the law and procedure applicable to these claims, (viii) the financial viability of the parties that contribute to the settlement of respirator claims, (ix) exhaustion of the insurance coverage maintained by certain of the parties that contribute to the settlement of respirator claims, or a change in the availability of the indemnity provided by a former owner of the business, (x) changes in the allocation of costs among the various parties paying legal and settlement costs, and (xi) a determination that the assumptions that were used to estimate Cabot’s share of liability are no longer reasonable. Other Matters The Company has various other lawsuits, claims and contingent liabilities arising in the ordinary course of its business and with respect to its divested businesses. The Company does not believe that any of these matters will have a material adverse effect on its financial position; however, litigation is inherently unpredictable. Cabot could incur judgments, enter into settlements or revise its expectations regarding the outcome of certain matters, and such developments could have a material impact on its results of operations in the period in which the amounts are accrued or its cash flows in the period in which the amounts are paid.

Commitments and Contingencies

9 Months Ended

Jun. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

G. Commitments and Contingencies

Contingencies

Respirator Liabilities

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

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

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

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

Other Matters

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