Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities - Freestanding Derivative (Details) - Other non-interest income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 21	$ 14	$ 31	$ 41
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	29	5	55	31
Interest rate contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	18	4	28	18
Interest rate contracts | Other interest rate exposures
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	(1)	11	(15)	32
Commodity contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	8	0	17	8
Foreign exchange contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	3	1	10	5
Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ (7)	$ (2)	$ (9)	$ (22)