Litigation, Claims and Contingencies - Summary of Reconciliation of Changes in Environmental Remediation Reserves (Details) - USD ($) $ in Millions	9 Months Ended
Jun. 30, 2021	Jun. 30, 2020
Loss Contingencies [Line Items]
Reserve - beginning of period	$ 200	$ 186
Disbursements	(35)	(28)
Revised obligation estimates and accretion	40	40
Reserve - end of period	$ 205	$ 198

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Amount of expense (reversal of expense) which increases (decreases) the accrual for environmental loss contingencies from revisions in estimates to existing obligations. Excludes changes related to business acquisitions, divestitures, or currency movement.

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Amount of cash outflow to settle environmental loss contingencies.

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