Commitments and Contingencies - Environmental Matters (Details) T in Millions, $ in Millions	1 Months Ended						12 Months Ended
	Sep. 30, 2016	Jan. 31, 2016	Dec. 31, 2015 USD ($)	Aug. 31, 2014	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2016 USD ($) T	Dec. 31, 2015 USD ($) T	Jun. 01, 2015 USD ($)
Electric | Cross-State Air Pollution Rule
Air Quality
Number Of States Impacted By Cross State Air Pollution Rule	23
Electric | Mercury and Other Hazardous Air Pollutants
Air Quality
Percentage mercury emission reduction							90.00%
Electric | Climate Change
Air Quality
Percentage greenhouse gas emission reduction nationwide								32.00%
Interim requirement greenhouse gas emissions reductions								0.667
Percentage carbon dioxide emission reduction company goal							40.00%
Carbon dioxide emissions | T							29.6	31.0
Electric | Clean Water Act Cooling Water Intake Structure Rule
Water Quality
Number of compliance options available to meet standard				7
Electric | Steam Electric Effluent Guidelines
Water Quality
Renewal period of facility permits		5 years
Electric | Steam Electric Effluent Guidelines | Minimum
Water Quality
Expected environmental costs to achieve required emission reductions							$ 80.0
Electric | Steam Electric Effluent Guidelines | Maximum
Water Quality
Expected environmental costs to achieve required emission reductions							$ 110.0
Electric | Weston and Pulliam Consent Decree | WPS
Consent Decrees
Beneficial environmental project amount						$ 6.0
Civil penalty						$ 1.2
Regulatory asset for undepreciated book value of retired plants									$ 11.5
Electric | Joint Ownership Power Plants Consent Decree - Columbia and Edgewater | WPS
Consent Decrees
Beneficial environmental project amount					$ 1.3
Civil penalty					$ 0.4
Natural gas | Climate Change
Air Quality
Carbon dioxide emissions | T							26.7	27.2
Natural gas | Manufactured Gas Plant Remediation
Manufactured Gas Plant Remediation
Regulatory assets recorded for remediation of manufactured gas plant sites			$ 697.0				$ 702.7	$ 697.0
Reserves recorded for remediation of manufactured gas plant sites			$ 628.0				$ 633.4	$ 628.0
WISCONSIN | Electric | Climate Change
Air Quality
Percentage greenhouse gas emission reduction state								41.00%
Percentage greenhouse gas emission reduction for retirement of a nuclear plant			10.00%
WISCONSIN | Electric | Renewables, Efficiency, and Conservation
Renewables, Efficiency, and Conservation
Percent renewable energy portfolio requirement for years 2016 through 2018							10.00%
Percent of annual operating revenues							1.20%
Percentage renewable portfolio requirement for years 2019 through 2020							12.50%
Percentage renewable portfolio requirement for 2021							15.00%
WISCONSIN | Electric | Renewables, Efficiency, and Conservation | WE
Renewables, Efficiency, and Conservation
Renewable energy percent required							8.27%
WISCONSIN | Electric | Renewables, Efficiency, and Conservation | WPS
Renewables, Efficiency, and Conservation
Renewable energy percent required							9.74%
MICHIGAN | Electric | Climate Change
Air Quality
Percentage greenhouse gas emission reduction state								39.00%
MICHIGAN | Electric | Renewables, Efficiency, and Conservation
Renewables, Efficiency, and Conservation
Percent renewable energy portfolio requirement for years 2016 through 2018							10.00%
MICHIGAN | Electric | Renewables, Efficiency, and Conservation | Maximum
Renewables, Efficiency, and Conservation
Energy optimization target							1.00%