Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities - Freestanding Derivative (Details) - Other Non-Interest Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 60	$ 99	$ 95
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	48	38	37
Interest rate contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	25	20	24
Interest rate contracts | Other interest rate exposures
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	33	61	67
Commodity contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	16	13	10
Foreign exchange contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	7	5	3
Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ (21)	$ 0	$ (9)