Regulatory Matters - Utility Rates (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 Bison Wind Energy Center [Member] MW	Dec. 31, 2013 Bison 4 Wind Project [Member] MW	Dec. 31, 2013 Municipal Customers [Member] Customers	Dec. 31, 2013 Non-Affiliated Private Utility [Member] Customers	Jun. 01, 2011 MPUC 2010 MN Rate Case [Member] Electric Rates [Member] Retail Customers [Member]	Dec. 31, 2013 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Municipal Customers [Member] Years Customers	Dec. 31, 2013 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Non-Affiliated Private Utility [Member] Customers MW	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	1		16	1
Average Monthly Demand (in MWs)							17
Length of Notice Required to Terminate (Years)						3
Generating Capacity (MW)	292	205
Estimated Capital Expenditures		$ 345
Capital Cost Spent to Date		$ 55.6