Customer Deposits - Categorized as Interest or Non-interest Bearing (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
U.S.:
Interest-bearing	$ 153,926	$ 151,425
Non-interest-bearing (includes Card Member credit balances of: 2026, $483; 2025, $556)	542	606
Non-U.S.:
Interest-bearing	22	18
Non-interest-bearing (includes Card Member credit balances of: 2026, $525; 2025, $436)	528	439
Total customer deposits	155,019	152,488
Card Member Credit Balances
U.S.:
Non-interest-bearing (includes Card Member credit balances of: 2026, $483; 2025, $556)	483	556
Non-U.S.:
Non-interest-bearing (includes Card Member credit balances of: 2026, $525; 2025, $436)	$ 525	$ 436