Fair Value (Nonrecurring Fair Value Measurements) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 269	$ 1,040
Level 2 [Member] | Loans Held For Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	8
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	261	1,040
Nonrecurring Assets - Gains (Losses)	(54)	6	(170)
Level 3 [Member] | Nonaccrual Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	54	35
Nonrecurring Assets - Gains (Losses)	(19)	(8)	(68)
Level 3 [Member] | Loans Held For Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value		224
Nonrecurring Assets - Gains (Losses)		(7)	(4)
Level 3 [Member] | Equity Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	17	6
Nonrecurring Assets - Gains (Losses)	(2)	1
Level 3 [Member] | Mortgage Servicing Rights [Member] | Commercial Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value		543
Nonrecurring Assets - Gains (Losses)		88	(5)
Level 3 [Member] | OREO and Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	168	181
Nonrecurring Assets - Gains (Losses)	(19)	(26)	(73)
Level 3 [Member] | Long-lived assets held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	22	51
Nonrecurring Assets - Gains (Losses)	$ (14)	$ (40)	$ (20)