Reserves for Credit Losses - Changes in Card Member Receivables Reserve for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 01, 2020	Jan. 01, 2020
Changes in the Card Member receivable reserve for losses
Provisions	$ 242	$ 230	$ 249
Card Member Receivables [Member]
Changes in the Card Member receivable reserve for losses
Balance, January 1	162	167	145
Provisions	224	216	243
Net write-offs	(177)	(229)	(238)
Other adjustments	8	8	17
Balance, December 31	70	162	167
Net of recoveries	82	125	119
Participation interests in financing receivables purchased from affiliates		2,700	9,800
Participation interest in financing receivables sold to affiliates		1,100	$ 6,200
Card Member Receivables [Member] | Global Consumer Services Group [Member]
Changes in the Card Member receivable reserve for losses
Removal of financing receivables				$ 7,200
Card Member Receivables [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Changes in the Card Member receivable reserve for losses
Balance, January 1	$ 15
Balance, December 31		$ 15
Decrease in financing receivable, allowance					$ 147