Reserves for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2020
Reserve for Losses [Roll Forward]
Provisions for credit losses	$ 4,730	$ 3,573	$ 3,352
Card Member Loans [Member]
Reserve for Losses [Roll Forward]
Beginning Balance	2,383	2,134	1,706
Provisions for credit losses	3,453	2,462	2,266
Ending Balance	5,344	2,383	2,134
Recoveries	568	525	444
Recoveries of bad debts - TDR	(134)	(79)	(33)
Card Member Loans [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Reserve for Losses [Roll Forward]
Beginning Balance	4,027
Ending Balance		4,027
Increase in financing receivable, allowance				$ 1,643
Provisions for financing receivable deductions net write offs principal [Member] | Card Member Loans [Member]
Reserve for Losses [Roll Forward]
Net write-offs	(1,795)	(1,860)	(1,539)
Provisions for financing receivable deductions net write offs interest and fees [Member] | Card Member Loans [Member]
Reserve for Losses [Roll Forward]
Net write-offs	(375)	(375)	(304)
Provisions for financing receivable losses other [Member] | Card Member Loans [Member]
Reserve for Losses [Roll Forward]
Other	34	22	5
Foreign Currency Translation Adjustments [Member] | Card Member Loans [Member]
Reserve for Losses [Roll Forward]
Reserves for credit losses - other	$ (35)	$ (4)	$ 11