Asset Quality (Nonperforming Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Nonperforming loans	$ 2,281	$ 2,126
Other real estate owned (OREO)	259	279
Foreclosed and other assets	12	20
Total OREO and foreclosed assets	271	299
Total nonperforming assets	$ 2,552	$ 2,425
Nonperforming loans to total loans	1.10%	1.03%
Nonperforming assets to total loans, OREO and foreclosed assets	1.23%	1.17%
Nonperforming assets to total assets	0.71%	0.68%
Mortgage loans in process of foreclosure	$ 500	$ 600
Government Insured or Guaranteed Loans [Member]
Mortgage loans in process of foreclosure	300	300
Total commercial lending [Member]
Nonperforming loans	732	545
Total consumer lending [Member]
Nonperforming loans	$ 1,549	$ 1,581