Divestitures	12 Months Ended
Sep. 30, 2021
Discontinued Operations And Disposal Groups [Abstract]
Divestitures	Note D. Divestitures Sale of Specialty Fluids Business In June 2019, the Company completed the sale of its Specialty Fluids business, an operating segment of the Company, to Sinomine (Hong Kong) Rare Metals Resources Co. Limited, a wholly owned subsidiary of Sinomine Resource Group Co., Ltd. for total proceeds of $133 million. The Company recognized a pre-tax loss on the sale of the Specialty Fluids business of $9 million in fiscal 2019 and a $20 million impairment charge during the second quarter of fiscal 2019. The sale was subject to customary post-closing adjustments, which were finalized during the second quarter of fiscal 2020 and resulted in an additional pre-tax loss on sale of $1 million. The sale of the Specialty Fluids business did not meet the criteria to be reported as a discontinued operation as it did not constitute a significant strategic business shift for the Company, and had no major effect on operations. Sale of Marshall Mine On September 30, 2020, the Company entered into an agreement to sell its lignite mine located in Marshall, Texas to ADA Carbon Solutions, LLC (“ADACS”) for a nominal amount. As part of the transaction, the Company agreed to fund a portion of the costs ADACS expects to incur to close the mine and included $9 million for these costs in Accounts payable and accrued liabilities and Other liabilities on the Consolidated Balance Sheets. The majority of these costs are to be paid within the next four years or at the time of a change of control of the business. At the same time, Cabot idled its activation kilns at its manufacturing facility in Marshall, Texas. The Company continues certain operational activities including washing of activated carbon, as well as packaging and warehousing operations at its Marshall facility. In fiscal 2020, the Company recognized a pre-tax loss on the sale of the mine of $67 million and an impairment charge to certain idled fixed assets of $62 million. In conjunction with the sale, the Company entered into a long-term supply agreement with ADACS, a producer of lignite-based activated carbon. Under the terms of this agreement, ADACS manufactures and supplies the Purification Solutions business’s proprietary portfolio of lignite-based activated carbon products exclusively to the Company.

Divestitures

12 Months Ended

Sep. 30, 2021

Discontinued Operations And Disposal Groups [Abstract]

Note D. Divestitures

Sale of Specialty Fluids Business

In June 2019, the Company completed the sale of its Specialty Fluids business, an operating segment of the Company, to Sinomine (Hong Kong) Rare Metals Resources Co. Limited, a wholly owned subsidiary of Sinomine Resource Group Co., Ltd. for total proceeds of $133 million. The Company recognized a pre-tax loss on the sale of the Specialty Fluids business of $9 million in fiscal 2019 and a $20 million impairment charge during the second quarter of fiscal 2019. The sale was subject to customary post-closing adjustments, which were finalized during the second quarter of fiscal 2020 and resulted in an additional pre-tax loss on sale of $1 million. The sale of the Specialty Fluids business did not meet the criteria to be reported as a discontinued operation as it did not constitute a significant strategic business shift for the Company, and had no major effect on operations.

Sale of Marshall Mine

On September 30, 2020, the Company entered into an agreement to sell its lignite mine located in Marshall, Texas to ADA Carbon Solutions, LLC (“ADACS”) for a nominal amount. As part of the transaction, the Company agreed to fund a portion of the costs ADACS expects to incur to close the mine and included $9 million for these costs in Accounts payable and accrued liabilities and Other liabilities on the Consolidated Balance Sheets. The majority of these costs are to be paid within the next four years or at the time of a change of control of the business. At the same time, Cabot idled its activation kilns at its manufacturing facility in Marshall, Texas. The Company continues certain operational activities including washing of activated carbon, as well as packaging and warehousing operations at its Marshall facility. In fiscal 2020, the Company recognized a pre-tax loss on the sale of the mine of $67 million and an impairment charge to certain idled fixed assets of $62 million.

In conjunction with the sale, the Company entered into a long-term supply agreement with ADACS, a producer of lignite-based activated carbon. Under the terms of this agreement, ADACS manufactures and supplies the Purification Solutions business’s proprietary portfolio of lignite-based activated carbon products exclusively to the Company.