COMMITMENTS AND CONTINGENCIES (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	1 Months Ended
	Sep. 30, 2013 Manufactured Gas Plant Remediation Natural Gas Utility site	Mar. 31, 2013 WPS Weston and Pulliam Plants Electric Utility	Jun. 30, 2013 WPS Columbia And Edgewater Electric Utility	Sep. 30, 2013 WPS WDNR Issued NOV's Electric Utility NOV	Sep. 30, 2013 WPS Mercury emission Electric Utility MW
Air Permitting Violation Claims
Beneficial environmental project amount		$ 6.0	$ 1.3
Civil penalty and/or legal fees		1.2	0.4
Number of NOV's alleging violations of the air permits received since 2008				4
Number of corrective actions taken for NOV's received				5
Mercury and Interstate Air Quality Rules
Percentage mercury reduction required by the State of Wisconsin's mercury rule through 2014					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 by 2015, required by the State of Wisconsin's mercury rule, for electric generating units above 150 MW					90.00%
Level of electric generating units above which a reduction in mercury emissions is required by the Best Available Control Technology rule (in MW)					25
Highest level of electric generating units for which a reduction in mercury emissions is required by the Best Available Control Technology rule (in MW)					150
Estimated capital cost to achieve required emission reduction					9
Manufactured Gas Plant Remediation
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	612.1
Cash expenditures for environmental remediation not yet recovered in rates	46.2
Regulatory assets recorded for cash and estimated future remediation expenditures, net of insurance recoveries received	658.3
Insurance recoveries received	$ 64.9