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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% |  |  |

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