Reserves for Credit Losses - Changes in Loan Reserve (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 01, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions		$ 5,185	$ 4,923	$ 2,182
Reversal of reserve for credit losses		(5,185)	(4,923)	(2,182)
Card Member loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance		5,118	3,747	3,305
Provisions	$ (49)	4,109	3,839	1,514
Other		(33)	18	(6)
Ending Balance		5,679	5,118	3,747
Reversal of reserve for credit losses	$ 49	(4,109)	(3,839)	(1,514)
Recoveries		730	537	539
Foreign currency translation adjustments		(33)	18	(6)
Card Member loans | Principal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs		(2,894)	(2,043)	(837)
Card Member loans | Interest and fees
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs		$ (621)	$ (443)	$ (229)