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]
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