U.S. and Europe Retrospective Responsibility Plans - Schedule of Changes in the U.S. Litigation Escrow Account (Details) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Escrow Account [Roll Forward]
Balance as of beginning of period	$ 2,990	$ 3,089
Deposits into the U.S. litigation escrow account	625	375
Balance as of end of period	665	2,926
Interest Income \| Opt-out Merchants
Escrow Account [Roll Forward]
Payments to opt-out merchants, net of interest earned on escrow funds	$ (2,950)	$ (538)

Amount of cash and cash equivalent restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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