Other Fees and Commissions and Other Expenses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Non Interest Income [Line Items]
Delinquency fees	$ 255	$ 232	$ 506	$ 474
Foreign currency conversion fee revenue	250	233	480	458
Loyalty Partner-related fees	109	107	223	218
Travel commissions and fees	121	112	229	211
Service fees	102	102	202	206
Other Fees and Commissions
Non Interest Income [Line Items]
Revenues and fees	$ 837	$ 786	$ 1,640	$ 1,567