Asset Quality (Nonperforming Assets) (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Total nonperforming loans	$ 1,873,000,000	$ 2,144,000,000
OREO and Foreclosed Assets	194,000,000	230,000,000
Total nonperforming assets	$ 2,067,000,000	$ 2,374,000,000
Nonperforming loans to total loans	0.85%	1.02%
Nonperforming assets to total loans, OREO and foreclosed assets	0.93%	1.12%
Nonperforming assets to total assets	0.55%	0.65%
Mortgage loans in process of foreclosure	$ 300,000,000	$ 400,000,000
Government Insured or Guaranteed Loans [Member]
Mortgage loans in process of foreclosure	200,000,000	200,000,000
Total commercial lending [Member]
Total nonperforming loans	550,000,000	655,000,000
Total consumer lending [Member]
Total nonperforming loans	$ 1,323,000,000	$ 1,489,000,000