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, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains (losses) recognized in earnings	$ 95	$ (40)	$ (72)
Derivatives designated as accounting hedges | Fair value hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings on derivatives	200	(550)	1
(Losses) gains recognized in earnings on hedged items	(157)	507	(37)
Net fair value hedge ineffectiveness gains (losses)	43	(43)	(36)
Derivatives not designated as accounting hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	52	3	(36)
Derivatives not designated as accounting hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	52	28	(17)
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	23	(12)	4
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	18	49	39
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	11	(9)	(60)
Derivatives not designated as accounting hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	1	(5)	(15)
Derivatives not designated as accounting hedges | Other contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as accounting hedges	$ (1)	$ (20)	$ (4)