XML 37 R62.htm IDEA: XBRL DOCUMENT v2.4.0.6
Credit Risk (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure $ 531  
Concentration Risk Credit Risk Financial Instrument Maximum Exposure Net 461  
Additional Collateral, Aggregate Fair Value 71 88
Collateral Already Posted, Aggregate Fair Value 145 110
Pledged Financial Instruments, Not Separately Reported, Securities for Letter of Credit Facilities 4 4
Derivative Liability, Fair Value, Amount Not Offset Against Collateral $ 277 $ 259
Investment Grade [Member] | Credit Concentration Risk [Member]
   
Concentration Risk, Percentage 81.00%  
Investment Grade [Member] | Counterparty, A [Member]
   
Concentration Risk, Percentage 11.00%