Fair Value (Nonrecurring Fair Value Measurements) (Details) (Fair Value, Measurements, Nonrecurring [Member], Level 3 [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 1,068		$ 1,068		$ 907
Nonrecurring Assets - Gains (Losses)	6	(95)	(11)	(178)
Nonaccrual Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	83		83		158
Nonrecurring Assets - Gains (Losses)	(9)	(42)	(10)	(96)
Loans Held For Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	209		209		315
Nonrecurring Assets - Gains (Losses)	(11)	(1)	(11)	(1)
Equity Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	6		6		12
Nonrecurring Assets - Gains (Losses)	(3)		(3)
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	519		519		191
Nonrecurring Assets - Gains (Losses)	60	(14)	73	(9)
OREO and Foreclosed Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	199		199		207
Nonrecurring Assets - Gains (Losses)	(19)	(32)	(33)	(59)
Long-lived assets held for sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	52		52		24
Nonrecurring Assets - Gains (Losses)	$ (12)	$ (6)	$ (27)	$ (13)