Reserves for Credit Losses (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions	$ 4,730	$ 3,573	$ 3,352
Card Member Receivables [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	619	573	521
Provisions	1,015	963	937
Net write-offs	(881)	(900)	(859)
Other	7	(17)	(26)
Ending Balance	267	619	573
Recoveries	386	374	367
Recoveries of bad debts - TDR	(47)	(16)	0
Card Member Receivables [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	126
Ending Balance		126
Decrease in financing receivable, allowance				$ 493
Card Member Receivables [Member] | Foreign Currency Translation Adjustments [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Reserves for credit losses - other	$ (5)	$ 0	$ 6