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Regulatory Matters - Electric Rates (Details) (USD $) In Millions, unless otherwise specified | Jun. 01, 2011 MPUC 2010 MN Rate Case [Member] Electric Rates [Member] Retail Customers [Member] | Jun. 30, 2012 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Municipal Customers [Member] Customers | Jun. 30, 2012 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Non-Affiliated Private Utility [Member] MW Customers | Jun. 30, 2012 PSCW 2012 Wisconsin Rate Case [Member] Retail Customers [Member] | Jan. 31, 2011 PSCW 2012 Wisconsin Rate Case [Member] Retail Customers [Member] | Jun. 30, 2012 PSCW 2012 Wisconsin Rate Case [Member] Electric Rates [Member] Retail Customers [Member] | Jun. 30, 2012 PSCW 2012 Wisconsin Rate Case [Member] Natural Gas Rates [Member] Retail Customers [Member] | Jun. 30, 2012 PSCW 2012 Wisconsin Rate Case [Member] Water Rates [Member] Retail Customers [Member]
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Approved Rate of Return on Common Equity | 10.38% |  |  |  | 10.90% |  |  |
Approved Percentage of Capital Structure Related to Equity | 54.29% |  |  |  |  |  |  |
Number of Customers |  | 16 | 1 |  |  |  |  |
Length of Notice Required to Terminate (in Years) |  | 3 | 2 |  |  |  |  |
Average Monthly Demand (in MWs) |  |  | 17 |  |  |  |  |
Requested Rate Increase |  |  |  | 2.50% |  | 1.20% | 0.70% | 13.40%
Requested Rate of Return on Common Equity |  |  |  | 10.90% |  |  |  |
Requested Percentage of Capital Structure Related to Equity |  |  |  | 55.00% |  |  |  |
Requested Percentage of Capital Structure Related to Debt |  |  |  | 45.00% |  |  |  |
Additional Revenue Generated from Rate Increase |  |  |  | $ 1.8 |  |  |  |

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