Reserves for Credit Losses - Changes in Loan Reserve (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions	$ 4,923	$ 2,182	$ (1,419)
Card Member loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,747	3,305	5,344
Provisions	3,839	1,514	(1,155)
Other	18	(6)	(5)
Ending Balance	5,118	3,747	3,305
Recoveries	537	539	657
Foreign currency translation adjustments	18	(6)	(6)
Card Member loans | Principal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs	(2,043)	(837)	(672)
Card Member loans | Interest and fees
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs	$ (443)	$ (229)	$ (207)