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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2011
Summary of Significant Accounting Policies [Abstract] |
Estimated average service lives [Table Text Block] | Depreciation is provided on the Company’s other classes of plant in service over their estimated average service lives, which are as follows (in years):
Production, excluding thermal: |
Hydro | 86 |
Wind | 27 |
Transmission | 53 |
Distribution | 40 |
General | 14 |

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