Fair Value Measurements - Summary of Financial Instruments Subject to Recurring Fair Value Measurements (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions		Jun. 30, 2022		Sep. 30, 2021
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Assets
Cash and cash equivalents		$ 629		$ 210
Restricted investments		407	[1],[2]	421	[3],[4]
Investment of captive insurance company		9	[5]	8	[6]
Foreign currency derivatives		2	[7]	1	[8]
Total assets at fair value		1,050		645
Liabilities
Foreign currency derivatives		3	[9]	2	[10]
Total liabilities at fair value		5
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Commodity Derivatives [Member]
Assets
Commodity derivatives		3	[7]	5	[8]
Liabilities
Commodity derivatives	[9]	2
Estimate of Fair Value, Fair Value Disclosure [Member]
Assets
Cash and cash equivalents		629		210
Restricted investments		407	[1],[2]	421	[3],[4]
Investment of captive insurance company		9	[5]	8	[6]
Foreign currency derivatives		2	[7]	1	[8]
Total assets at fair value		1,050		645
Liabilities
Foreign currency derivatives		3	[9]	2	[10]
Total liabilities at fair value		5
Estimate of Fair Value, Fair Value Disclosure [Member] | Commodity Derivatives [Member]
Assets
Commodity derivatives		3	[7]	5	[8]
Liabilities
Commodity derivatives	[9]	2
Fair Value, Inputs, Level 1 [Member]
Assets
Cash and cash equivalents		629		210
Restricted investments		407	[1],[2]	421	[3],[4]
Investment of captive insurance company		9	[5]	8	[6]
Foreign currency derivatives		0	[7]	0	[8]
Total assets at fair value		1,045		639
Liabilities
Foreign currency derivatives		0	[9]	0	[10]
Total liabilities at fair value		0
Fair Value, Inputs, Level 1 [Member] | Commodity Derivatives [Member]
Assets
Commodity derivatives		0	[7]	0	[8]
Liabilities
Commodity derivatives	[9]	0
Fair Value, Inputs, Level 2 [Member]
Assets
Cash and cash equivalents		0		0
Restricted investments		0	[1],[2]	0	[3],[4]
Investment of captive insurance company		0	[5]	0	[6]
Foreign currency derivatives		2	[7]	1	[8]
Total assets at fair value		5		6
Liabilities
Foreign currency derivatives		3	[9]	2	[10]
Total liabilities at fair value		5
Fair Value, Inputs, Level 2 [Member] | Commodity Derivatives [Member]
Assets
Commodity derivatives		3	[7]	5	[8]
Liabilities
Commodity derivatives	[9]	2
Fair Value, Inputs, Level 3 [Member]
Assets
Cash and cash equivalents		0		0
Restricted investments		0	[1],[2]	0	[3],[4]
Investment of captive insurance company		0	[5]	0	[6]
Foreign currency derivatives		0	[7]	0	[8]
Total assets at fair value		0		0
Liabilities
Foreign currency derivatives		0	[9]	0	[10]
Total liabilities at fair value		0
Fair Value, Inputs, Level 3 [Member] | Commodity Derivatives [Member]
Assets
Commodity derivatives		0	[7]	$ 0	[8]
Liabilities
Commodity derivatives	[9]	$ 0

[1] Included in restricted investments and $61 million within other current assets in the Condensed Consolidated Balance Sheets

[2] Includes $269 million related to the Asbestos trust and $138 million related to the Environmental trust

[3] Included in restricted investments and $37 million within other current assets in the Condensed Consolidated Balance Sheets

[4] Includes $333 million related to the Asbestos trust and $88 million related to the Environmental trust

[5] Included in other noncurrent assets in the Condensed Consolidated Balance Sheets

[6] Included in other noncurrent assets in the Condensed Consolidated Balance Sheets

[7] Included in accounts receivable in the Condensed Consolidated Balance Sheets

[8] Included in accounts receivable in the Condensed Consolidated Balance Sheets

[9] Included in accrued expenses and other liabilities in the Condensed Consolidated Balance Sheets.

[10] Included in accrued expenses and other liabilities in the Condensed Consolidated Balance Sheets.