Derivative Financial Instruments (Schedule of Unrealized Gains or Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	$ 48	$ 12	$ (9)	$ 46
Futures | Net return (loss) on mortgage servicing rights
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	0	1	0	4
Interest rate swaps | Net return (loss) on mortgage servicing rights
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	3	13	(5)	28
Interest rate swaps | Other noninterest income
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	1	(1)	1	1
Mortgage backed securities forwards | Net return (loss) on mortgage servicing rights
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	3	5	3	13
Rate lock commitments and forward agency and loan sales | Net (loss) gain on loan sales
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	41	(6)	(8)	(1)
Rate lock commitments | Other noninterest income
Derivative [Line Items]
Net gain (loss) recognized in income on derivative instruments	$ 0	$ 0	$ 0	$ 1