Customer Deposits (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
U.S.:
Interest-bearing	$ 72,445	$ 69,144
Non-interest-bearing	415	412
Non-U.S.:
Interest-bearing	23	28
Non-interest-bearing	404	376
Total customer deposits	73,287	69,960
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	389	376
Non-U.S.:
Non-interest-bearing	$ 401	$ 367