Fair Value Disclosures (Fair Value Measured on Nonrecurring Basis) (Details) (Fair Value, Measurements, Nonrecurring [Member], Level 3 [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans (excluding acquired from FDIC)	$ 109	$ 50
Valuation adjustments to impaired loans (excluding acquired from FDIC)	(52)	(41)
Foreclosed real estate (excluding acquired from FDIC)	87	71
Valuation adjustments on foreclosed real estate (excluding acquired from FDIC)	$ 1	$ (6)