Reserves for Credit Losses - Changes in Loan Reserve (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	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 Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance		5,592	5,271	5,679	5,118	$ 5,118
Provisions for credit losses	$ (144)	1,094	970	1,995	1,984
Other		19	(7)	27	(13)
Ending Balance	$ 5,767	5,767	5,321	5,767	5,321	$ 5,679
Card Member Loans | Principal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs		(771)	(753)	(1,589)	(1,458)
Recoveries		242	179	463	338
Card Member Loans | Interest and fees
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs		$ (167)	$ (160)	$ (345)	$ (310)