Mortgage Banking Activities, Managed Servicing Portfolio (Details) - USD ($) $ in Billions	Sep. 30, 2016	Dec. 31, 2015
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,703	$ 1,778
Total managed servicing portfolio	$ 2,197	$ 2,256
Ratio of MSRs to related loans serviced for others	0.69%	0.77%
Residential mortgage servicing rights [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,226	$ 1,300
Owned loans serviced	352	345
Subserviced for others	4	4
Total managed servicing portfolio	1,582	1,649
Commercial mortgage servicing [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	477	478
Owned loans serviced	130	122
Subserviced for others	8	7
Total managed servicing portfolio	$ 615	$ 607