Reserves for Credit Losses - Changes in Receivables Reserve (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions for credit losses	$ 1,150	$ 1,269
Card Member Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	171	174	$ 174
Provisions for credit losses	146	196
Net write-offs	(169)	(217)
Other	0	(2)
Ending Balance	148	151	$ 171
Recoveries	$ 73	$ 76