Derivative Instruments and Hedging Activities - Net Gains (Losses) Recognized in Earnings Related to Derivatives in Fair Value Hedging Relationships and Free-Standing Derivatives (Details) - Other Non-Interest Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains recognized in earnings	$ 103	$ 85	$ 75
Derivatives designated as accounting hedges | Fair value hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings on derivatives	(212)	(613)	(66)
Gains (losses) recognized in earnings on hedged items	216	603	75
Net fair value hedge ineffectiveness gains (losses)	4	(10)	9
Derivatives not designated as accounting hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	99	95	66
Derivatives not designated as accounting hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	99	104	68
Derivatives not designated as accounting hedges | Interest rate contracts | MSRs
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	3	(1)	3
Derivatives not designated as accounting hedges | Interest rate contracts | Customer accommodation
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	38	37	21
Derivatives not designated as accounting hedges | Interest rate contracts | Other interest rate exposures
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	58	68	44
Derivatives not designated as accounting hedges | Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ 0	$ (9)	$ (2)