|
Credit Risk (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
6 Months Ended | |
|---|---|---|
|
Jun. 30, 2012
|
Dec. 31, 2011
|
|
| Concentration risk, cedit rsk, fnancial istrument, mximum exposure | $ 464 | |
| Concentration risk credit risk financial instrument maximum exposure net | 424 | |
| Additional collateral, aggregate fair value | 32 | 88 |
| Collateral already posted, aggregate fair value | 5 | 110 |
| Pledged financial instruments, not separately reported, securities for letter of credit facilities | 3 | 4 |
| Derivative liability, fair value, amount not offset against collateral | $ 146 | $ 259 |
|
Investment Grade | Credit Concentration Risk [Member]
|
||
| Concentration risk, percentage (percentage) | 62.00% | |
|
Investment Grade | Counterparty, A
|
||
| Concentration risk, percentage (percentage) | 10.00% |