Accumulated Other Comprehensive Income (Loss) - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Tax (benefit) expense included in net unrealized gains (losses), investment securities	$ 70	$ 135	$ 134	$ 308
Tax included in reclassification, investment securities	(7)	(13)	(9)	(24)
Tax included in amortization, investment securities	2	4	5	7
Cumulative effect of new accounting principle in period of adoption, tax					$ 103	$ 0
Tax (benefit) expense included in net unrealized gains (losses), fair value option liabilities	(6)	0	(52)	0
Tax (benefit) expense included in net unrealized gains (losses), cash flow hedges	(3)	(10)	(4)	(38)
Tax included in reclassification, cash flow hedges	$ 1	$ 2	$ 2	$ 3