Reserves for Credit Losses - Changes in Receivables Reserve (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions for credit losses	$ 1,287	$ 1,356	$ 3,842	$ 3,893
Card Member Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	193	171	171	174	$ 174
Provisions for credit losses	190	170	562	592
Net write-offs	(183)	(187)	(536)	(609)
Other	0	2	3	(1)
Ending Balance	200	156	200	156	$ 171
Recoveries	$ 77	$ 74	$ 224	$ 228