Fair Value (Nonrecurring Fair Value Measurements) (Details) - Types of Financial Instruments [Domain] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 162		$ 162
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value					$ 269
Fair Value, Measurements, Nonrecurring [Member] | 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
Nonrecurring Assets - Gains (Losses)		$ (1)		$ (1)
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value					261
Nonrecurring Assets - Gains (Losses)	(32)	(28)	(46)	(43)
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	33		33		54
Nonrecurring Assets - Gains (Losses)	(15)	(11)	(15)	(15)
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Equity Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value					17
Nonrecurring Assets - Gains (Losses)		(3)		(3)
Fair Value, Measurements, Nonrecurring [Member] | 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	110		110		168
Nonrecurring Assets - Gains (Losses)	(12)	(7)	(18)	(15)
Fair Value, Measurements, Nonrecurring [Member] | 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	19		19		$ 22
Nonrecurring Assets - Gains (Losses)	$ (5)	$ (6)	$ (13)	$ (9)