Asset Quality (Nonperforming Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Total nonperforming loans	$ 1,694	$ 1,865
OREO and Foreclosed Assets	131	170
Total nonperforming assets	$ 1,825	$ 2,035
Nonperforming loans to total loans	0.76%	0.85%
Nonperforming assets to total loans, OREO and foreclosed assets	0.82%	0.92%
Nonperforming assets to total assets	0.48%	0.53%
Total commercial lending [Member]
Total nonperforming loans	$ 393	$ 554
Total consumer lending [Member]
Total nonperforming loans	$ 1,301	$ 1,311