Reserves for Credit Losses - Changes in Receivables Reserve (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions for credit losses	$ 1,405	$ 1,268	$ 2,555	$ 2,537
Card Member Receivables
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	148	151	171	174	$ 174
Provisions for credit losses	226	226	372	422
Net write-offs	(184)	(205)	(353)	(422)
Other	3	(1)	3	(3)
Ending Balance	193	171	193	171	$ 171
Recoveries	$ 74	$ 78	$ 147	$ 154