Derivatives - Economic Hedges (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Other
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	$ 13	$ (3)
Interest rate lock commitments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	260	173
Mortgage banking income \| Interest rate risk on mortgage banking income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	296	180
Other income \| Credit risk on loans
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	(27)	(6)
Other income \| Interest rate and foreign currency risk on ALM activities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	(319)	(598)
Personnel expense \| Price risk on restricted stock awards
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives not designated as hedging	$ (470)	$ 364