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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Sep. 30, 2013
Accounting Policies [Abstract] |
Property, Plant, and Equipment Depreciation Rates | Average depreciation rates by asset class are as follows:
Property, Plant, and Equipment Depreciation Rates At September 30 (percent)
| 2013 |  | 2012 |  | 2011
Asset Class |
Nuclear | 2.86 |  |  | 2.71 |  |  | 2.58 |
Coal-Fired | 3.47 |  |  | 5.65 |  |  | 3.80 |
Hydroelectric | 1.30 |  |  | 1.35 |  |  | 1.43 |
Gas and oil-fired | 3.21 |  |  | 3.67 |  |  | 3.70 |
Transmission | 2.76 |  |  | 2.99 |  |  | 3.39 |
Other | 8.14 |  |  | 8.10 |  |  | 7.39 |

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- Definition Tabular disclosure of average depreciation rates by asset class. + References No definition available. + Details
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