Fair Value (Fair Value Measurements- Nonrecurring Quantitative Information) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 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 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value		261
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	143	215
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	54
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	14	25
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member] | LGD percentage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 19	$ 29
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member] | LGD percentage [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss Severity	10.90%	2.90%
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member] | LGD percentage [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss Severity	99.20%	68.50%
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Nonaccrual Loans [Member] | LGD percentage [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss Severity	44.10%	42.10%
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
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Equity Investments [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market rate of return		6.00%
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Equity Investments [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market rate of return		6.00%
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Equity Investments [Member] | Discounted Cash Flow [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market rate of return		6.00%
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	$ 168
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | OREO and Foreclosed Assets [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	110	168
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	22
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Long-lived assets held for sale [Member] | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Nonrecurring Assets - Fair Value	$ 19	$ 22