Mortgage Banking Activities, Managed Servicing Portfolio (Details) - USD ($) $ in Billions	Jun. 30, 2017	Dec. 31, 2016
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,664	$ 1,684
Total managed servicing portfolio	$ 2,149	$ 2,179
Ratio of MSRs to related loans serviced for others	0.85%	0.85%
Residential mortgage servicing rights [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,189	$ 1,205
Owned loans serviced	343	347
Subserviced for others	4	8
Total managed servicing portfolio	1,536	1,560
Commercial mortgage servicing [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	475	479
Owned loans serviced	130	132
Subserviced for others	8	8
Total managed servicing portfolio	$ 613	$ 619