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Regulatory Matters - Utility Rates (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014 Hydro Project [Member]	Jun. 30, 2014 Bison Wind Energy Center [Member] MW	Jun. 30, 2014 Bison 4 [Member] MW	Jun. 01, 2011 MPUC 2010 Minnesota Rate Case [Member] Electric Rates [Member] Retail Customers [Member]	Jun. 30, 2014 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Municipal Customers [Member] Years Customers	Dec. 31, 2012 PSCW 2012 Wisconsin Rate Case [Member] Retail Customers [Member]
Rate Regulation [Line Items]
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
Length of Notice Required to Terminate (in Years)					3
Generating Capacity (MW)		292	205
Estimated Capital Expenditures, Including Past Expenditures	$ 90		$ 345
Capital Cost Spent to Date	$ 75.5		$ 246.6

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- Definition

Percentage of capital structure related to equity approved by the regulatory commission through a rate case proceeding.

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- Definition

Rate of return on common equity approved by the regulatory commission through a rate case proceeding.

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- Definition

Capital cost spent to date for project.

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- Definition

The estimated amount of certain capital expenditures related to environmental compliance, regulatory matters, or other commitments and/or contingencies. This estimate includes expenditures expected in future periods and expenditures made through the end of the current period.

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- Definition

Capacity of a generating facility, unit, or project in megawatts.

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- Definition

The length of notice required to terminate a contract (in years).

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- Definition

Number of Customers

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