COMMITMENTS AND CONTINGENCIES (Details 2) (USD $) In Millions, unless otherwise specified		6 Months Ended	1 Months Ended
	Jun. 30, 2013 Mercury emission MW	Jun. 30, 2013 Manufactured Gas Plant Remediation site	Mar. 31, 2013 WPS Weston and Pulliam Plants	Jun. 30, 2013 WPS Columbia And Edgewater	Jun. 30, 2013 WPS WDNR Issued NOV's NOV	Jun. 30, 2013 WPS Mercury emission
Environmental
Beneficial environmental project amount			$ 6.0	$ 1.3
Civil penalty			1.2
Civil penalty and legal fees				0.4
Environmental
Number of NOV's alleging violations of the air permits received since 2008					4
Number of corrective actions taken for NOV's received					5
Environmental
Percentage mercury reduction required by Best Available Control Technology rule	40.00%
Level of electric generating units above which a 90% reduction in mercury emissions is required by 2015 (in MW)	150
Percentage mercury reduction, required by Best Available Control Technology rule	90.00%
Level of electric generating units above which a reduction in mercury emissions (in MW)	25
Estimated capital cost to achieve required emission reduction						8
Environmental remediation obligations
Number of environmental remediation sites		53
Number of environmental remediation sites transferred to the EPA Superfund Alternative Sites Program		20
Estimated and accrued future undiscounted investigation and cleanup costs for all sites		628.1
Cash expenditures for environmental remediation not yet recovered in rates		35.4
Regulatory assets recorded for cash and estimated future remediation expenditures, net of insurance recoveries received		663.5
Insurance recoveries received		$ 63.1