Derivatives and Hedging Activities (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Derivative [Line Items]  
Additional collateral $ 94
Credit Rating Did Not Meet Specified Threshold [Member]  
Derivative [Line Items]  
Cash collateral posted 4
Interest Expense [Member]  
Derivative [Line Items]  
Cash flow hedge loss to be reclassified to earnings within twelve months $ 40
Securitized Debt [Member]  
Derivative [Line Items]  
Initial maximum period for cash flow hedges (in years) 5 years
Deposits [Member]  
Derivative [Line Items]  
Initial maximum period for cash flow hedges (in years) 7 years