Derivative Financial Instruments (Schedule of Unrealized Gains or Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	$ (5)	$ 4	$ 15	$ 4
U.S. Treasury and euro dollar futures | Net return on mortgage servicing asset
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	(3)	3	3	6
Swap futures | Net return on mortgage servicing asset
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	(9)	0	(8)	0
Mortgage backed securities forwards | Net return on mortgage servicing asset
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	(2)	2	0	4
Rate lock commitments and forward agency and loan sales | Net gain on loan sales
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	9	(2)	20	(7)
Interest rate swaps | Other noninterest income
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	$ 0	$ 1	$ 0	$ 1