Commitments and Contingencies - Schedule of Loss Contingencies by Contingency (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2023	Sep. 30, 2022
Loss Contingencies [Line Items]
Reserve for environmental liabilities, current	$ 42	$ 66
Reserve for environmental liabilities, noncurrent	223	220
Total reserves for environmental liabilities	265	286
Total asbestos-related liabilities	428	438
Total asbestos-related assets	312	300
Net asbestos-related liabilities	116	138
Restricted
Insurance receivables for asbestos-related liabilities	53	55
Total self-insured liabilities	347	341
Insurance receivables, current	10	10
Insurance receivables, noncurrent	20	20
Total insurance receivables	30	30
Asbestos Issue
Loss Contingencies [Line Items]
Total asbestos-related assets	259	245
Restricted
Cash	6	6
Investments	253	239
Other current liabilities
Loss Contingencies [Line Items]
Total asbestos-related liabilities	58	58
Restricted
Total self-insured liabilities	92	89
Other noncurrent liabilities
Loss Contingencies [Line Items]
Total asbestos-related liabilities	370	380
Restricted
Total self-insured liabilities	233	230
Other current assets
Loss Contingencies [Line Items]
Total asbestos-related assets	37	37
Other noncurrent assets
Loss Contingencies [Line Items]
Total asbestos-related assets	275	263
Accrued compensation and benefits
Restricted
Total self-insured liabilities	$ 22	$ 22