Regulatory Matters - Electric Rates (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 Municipal Customers [Member] Customers	Dec. 31, 2012 Non-Affiliated Private Utility [Member] Customers	Jun. 01, 2011 MPUC 2010 MN Rate Case [Member] Electric Rates [Member] Retail Customers [Member]	Dec. 31, 2012 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Municipal Customers [Member] Years Customers	Dec. 31, 2012 FERC-Approved Wholesale Rates [Member] Electric Rates [Member] Non-Affiliated Private Utility [Member] Years MW Customers	Dec. 31, 2012 PSCW 2012 Wisconsin Rate Case [Member] Retail Customers [Member]	Dec. 31, 2012 PSCW 2012 Wisconsin Rate Case [Member] Natural Gas Rates [Member] Retail Customers [Member]	Dec. 31, 2012 PSCW 2012 Wisconsin Rate Case [Member] Electric Rates [Member] Retail Customers [Member]	Dec. 31, 2012 PSCW 2012 Wisconsin Rate Case [Member] Water Rates [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
Length of Notice Required to Terminate (Years)				3	2
Average Monthly Demand (in MWs)					17
Approved Rate Increase or Decrease						2.40%	(2.00%)	1.20%	13.80%
Amount Of Estimated Additional Revenue						$ 1.7