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Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables) | 12 Months Ended
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Dec. 31, 2011
Regulatory Assets [Line Items] |
Schedule of Regulatory Assets and Liabilities [Table Text Block] | Regulatory assets and liabilities consist of the following (dollars in millions):
| Weighted Average Remaining Life (1) |  | As of December 31,
| 2011 |  | 2010
| Current |  | Noncurrent |  | Current |  | Noncurrent
Regulatory assets: |  |  |  |  |  |  |  |  |
| Price risk management (2) | 2 years |  | $ | 194 |  |  | $ | 172 |  |  | $ | 175 |  |  | $ | 185 |
| Pension and other postretirement plans (2) | (3) |  | — |  |  | 295 |  |  | — |  |  | 213 |
| Deferred income taxes (2) | (4) |  | — |  |  | 87 |  |  | — |  |  | 95 |
| Deferred broker settlements (2) | 1 year |  | 11 |  |  | — |  |  | 24 |  |  | — |
| Renewable energy deferral | 1 year |  | 1 |  |  | — |  |  | 22 |  |  | — |
| Debt reacquisition costs (2) | 7 years |  | — |  |  | 28 |  |  | — |  |  | 23 |
| Other (5) | Various |  | 10 |  |  | 12 |  |  | — |  |  | 28 |
| Total regulatory assets |  |  | $ | 216 |  |  | $ | 594 |  |  | $ | 221 |  |  | $ | 544 |
Regulatory liabilities: |  |  |  |  |  |  |  |  |
| Asset retirement removal costs (6) | (4) |  | $ | — |  |  | $ | 637 |  |  | $ | — |  |  | $ | 588 |
| Asset retirement obligations (6) | (4) |  | — |  |  | 36 |  |  | — |  |  | 33 |
| Power cost adjustment mechanism | (7) |  | — |  |  | 10 |  |  | — |  |  | — |
| Trojan ISFSI pollution control tax credits | (7) |  | — |  |  | 7 |  |  | 18 |  |  | 4 |
| Other | Various |  | 6 |  |  | 30 |  |  | 7 |  |  | 32 |
| Total regulatory liabilities |  |  | $ | 6 |  |  | $ | 720 |  |  | $ | 25 |  |  | $ | 657 |
(1) | As of December 31, 2011.
(2) | Does not include a return on investment.
(3) | Recovery expected over the average service life of employees. For additional information, see Note 2, Summary of Significant Accounting Policies.
(4) | Recovery expected over the estimated lives of the assets.
(5) | Of the total other unamortized regulatory asset balances, a return is recorded on $21 million and $26 million as of December 31, 2011 and 2010, respectively.
(6) | Included in rate base for ratemaking purposes.
(7) | Refund period not yet determined.

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- Definition Tabular disclosure of assets and liabilities that are created in connection with regulatory accounting [Table Text Block] + References No definition available. + Details
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