Reserves for Credit Losses - Changes in Receivables Reserve (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions for credit losses	$ 1,356	$ 1,233	$ 3,893	$ 3,486
Card Member Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	171	210	174	229
Provisions for credit losses	170	206	592	658
Net write-offs	(187)	(241)	(609)	(714)
Other	2	(1)	(1)	1
Ending Balance	156	174	156	174
Recoveries	$ 74	$ 73	$ 228	$ 218