Commitments and Contingencies - Environmental Matters (Details) T in Millions, $ in Millions	1 Months Ended			12 Months Ended	15 Months Ended
	Jun. 30, 2021 area	May 31, 2021	Dec. 31, 2020 USD ($) micrograms performance_obligations	Dec. 31, 2021 USD ($) performance_obligations T MW	Mar. 31, 2019 MW	Oct. 31, 2021 performance_obligations	Feb. 28, 2021 compliance_option
Manufactured Gas Plant Remediation
Regulatory asset			$ 3,544.1	$ 3,367.1
Environmental remediation costs
Manufactured Gas Plant Remediation
Regulatory asset			$ 638.2	$ 630.9
National Ambient Air Quality Standards | Electric
Air Quality
Number of changes to the 2015 ozone standards | performance_obligations						0
Number of counties to have boundaries revised | area	13
Number of nonattainment areas as designated by the EPA | area	6
Number of revisions necessary to meet the 2012 standard for particulate matter | performance_obligations			0
Current level of micrograms per cubic meter that particulate matter needs to be below | micrograms			12
National Ambient Air Quality Standards | Electric | Minimum
Air Quality
New possible number of micorgrams per cubic meter that particulate matter may be lowered to | micrograms			10
National Ambient Air Quality Standards | Electric | Maximum
Air Quality
New possible number of micorgrams per cubic meter that particulate matter may be lowered to | micrograms			11
Climate Change | Electric
Air Quality
Number of rules that regulate GHG emissions from electric generating units | compliance_option							0
Capacity of coal generation retired since the beginning of 2018, in megawatts | MW					1,800
Capacity of fossil-fueled generation to be retired by 2025, in megawatts | MW				1,600
Company near-term goal for percentage carbon dioxide emission reduction goal by 2025		60.00%
Company goal for percentage of carbon dioxide emissions reduction below 2005 levels by 2030		80.00%
Carbon dioxide emissions | T				22.0
Climate Change | Natural gas
Air Quality
Carbon dioxide emissions | T				23.6
Steam Electric Effluent Guidelines | Electric
Water Quality
Number of new ELG rule requirements that affect our electric utilities | performance_obligations				2
Expected capital investment to achieve required discharge limits				$ 110.0
Manufactured Gas Plant Remediation | Natural gas
Manufactured Gas Plant Remediation
Reserves for future environmental remediation of manufactured gas plant sites			$ 532.9	532.6
Manufactured Gas Plant Remediation | Natural gas | Environmental remediation costs
Manufactured Gas Plant Remediation
Regulatory asset			$ 638.2	$ 630.9
Renewables, Efficiency, and Conservation | Electric | Wisconsin
Renewables, Efficiency, and Conservation
Annual state renewable portfolio requirement, as a percent				10.00%
Percent of annual operating revenues used to fund renewable program				1.20%
Renewables, Efficiency, and Conservation | Electric | Wisconsin | WE
Renewables, Efficiency, and Conservation
Required renewable energy percent achieved				8.27%
Renewables, Efficiency, and Conservation | Electric | Wisconsin | WPS
Renewables, Efficiency, and Conservation
Required renewable energy percent achieved				9.74%
Renewables, Efficiency, and Conservation | Electric | Michigan
Renewables, Efficiency, and Conservation
Annual state renewable portfolio requirement for 2019 and 2020, as a percent				12.50%
Energy optimization target, as a percent				1.00%
Percentage renewable portfolio requirement 2021 and beyond				15.00%