Customer Deposits (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
U.S.:
Interest-bearing	$ 83,823	$ 85,583
Non-interest-bearing (includes Card Member credit balances of: 2021, $442; 2020, $576)	466	599
Non-U.S.:
Interest-bearing	19	19
Non-interest-bearing (includes Card Member credit balances of: 2021, $593; 2020, $671)	597	674
Total customer deposits	84,905	86,875
Card Member Credit Balances
U.S.:
Non-interest-bearing (includes Card Member credit balances of: 2021, $442; 2020, $576)	442	576
Non-U.S.:
Non-interest-bearing (includes Card Member credit balances of: 2021, $593; 2020, $671)	$ 593	$ 671