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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES PROPERTY, PLANT, AND EQUIPMENT (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Property, plant and equipment      
Gain (loss) on retirement of utility property, excluding land 0wps_GainLossOnOrdinaryRetirementOfPropertyExcludingLand    
Software | Minimum      
Property, plant and equipment      
Useful life 3 years    
Software | Maximum      
Property, plant and equipment      
Useful life 5 years    
Electric      
Property, plant and equipment      
Annual utility composite depreciation rate (as a percent) 2.73%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_ElectricMember		 2.79%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_ElectricMember		 2.87%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_ElectricMember
Natural gas      
Property, plant and equipment      
Annual utility composite depreciation rate (as a percent) 2.17%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_NaturalGasMember		 2.19%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_NaturalGasMember		 2.21%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService
/ us-gaap_PublicUtilityAxis
= wps_NaturalGasMember