Legal Proceedings, Contingencies and Commitments (Credit Commitments) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Mortgage loans interest-rate lock commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	$ 5,208	$ 4,115
Warehouse loan commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	1,400	1,670
Commercial and industrial commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	678	424
Other commercial commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	814	651
HELOC commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	217	179
Other consumer commitments
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	46	57
Standby and commercial letters of credit
Loss Contingencies [Line Items]
Unused Commitments to Extend Credit	$ 44	$ 30