Mortgage Banking Activities, Managed Servicing Portfolio (Details) - USD ($) $ in Billions	Jun. 30, 2019	Dec. 31, 2018
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,655	$ 1,707
Total managed servicing portfolio	$ 2,132	$ 2,175
Ratio of MSRs to related loans serviced for others	0.82%	0.94%
Residential mortgage servicing rights [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	$ 1,107	$ 1,164
Owned loans serviced	340	334
Subserviced for others	5	4
Total managed servicing portfolio	1,452	1,502
Commercial mortgage servicing [Member]
Components of Managed Servicing Portfolio [Abstract]
Serviced for others	548	543
Owned loans serviced	123	121
Subserviced for others	9	9
Total managed servicing portfolio	$ 680	$ 673