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Variable Interest Entities (VIEs) (Details) (Riverside Energy Center PPA [Member], USD $)
In Millions, unless otherwise specified |
3 Months Ended | 9 Months Ended | 1 Months Ended | ||
|---|---|---|---|---|---|
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Sep. 30, 2012
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Sep. 30, 2011
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Sep. 30, 2012
MW
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Sep. 30, 2011
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Apr. 30, 2012
Public Service Commission Of Wisconsin [Member]
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| Variable Interest Entity [Line Items] | |||||
| Costs, excluding fuel costs | $ 29.7 | $ 28.5 | $ 57.7 | $ 55.4 | |
| Approval of business acquisition purchase price | $ 393 | ||||
| Amount of electricity output (in megawatts) | 490 | ||||