Asset Quality (Summary of TDRs) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings (TDRs)	$ 2,448	$ 2,351
Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings (TDRs)	1,240	1,119
Accruing [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings (TDRs)	1,208	1,232
Total commercial lending [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings (TDRs)	588	434
Total consumer lending [Member]
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings (TDRs)	$ 1,860	$ 1,917