|
Fair Value (Details 7) (USD $)
In Millions, unless otherwise specified |
Sep. 30, 2012
|
Dec. 31, 2011
|
|---|---|---|
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||
| Nuclear decommissioning trusts | $ 1,029 | $ 937 |
| Unrealized Gains | 153 | 102 |
|
Equity securities [Member]
|
||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||
| Equity securities | 615 | 533 |
| Unrealized Gains | 124 | 80 |
|
Debt securities [Member]
|
||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||
| Debt securities | 405 | 385 |
| Unrealized Gains | 29 | 22 |
|
Cash and cash equivalents [Member]
|
||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||
| Cash and cash equivalents | 9 | 19 |
| Unrealized Gains | $ 0 | $ 0 |