Derivative Instruments and Hedging Activities - Net Gains (Losses) Related to Derivatives Designated as Cash Flow Hedges and Fair Value Hedges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 60	$ 99	$ 95
Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	48	38	37
Interest rate contracts | Customer accommodation | Other Non-Interest Income
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 | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	33	61	67
Foreign exchange contracts | Customer accommodation | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 7	5	3
Derivatives designated as accounting hedges
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains (losses) recognized in net income		110	191
Derivatives designated as accounting hedges | Fair value hedges | Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments		(212)	(613)
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge		216	603
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net		4	(10)
Derivatives designated as accounting hedges | Cash flow hedges | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		108	195
Derivatives designated as accounting hedges | Cash flow hedges | Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges		2	(4)
Derivatives designated as accounting hedges | Cash flow hedges | Interest rate contracts | Customer accommodation | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax		91	192
Derivatives designated as accounting hedges | Cash flow hedges | Foreign exchange contracts | Other interest rate exposures | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges		$ 17	$ 3