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Regulatory Environment (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
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May 31, 2018 USD ($) MW solar_projects | Mar. 31, 2018 USD ($) | Feb. 28, 2018 USD ($) Filings | Dec. 31, 2017 USD ($) | Nov. 30, 2017 USD ($) | Oct. 31, 2017 wind_turbines utility MW | Sep. 30, 2017 USD ($) utility | Jan. 31, 2017 | Oct. 31, 2016 USD ($) | Aug. 31, 2016 MW | Mar. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2018 USD ($) customer Assurance | Dec. 31, 2018 USD ($) customer change Assurance | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6.9 | $ 4.9 | $ 10.9
WE |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1.5 | 1.2 | 1.7
WE | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  | 10.20% |  |  |  |  |  |  |  |  |
Income Statement impact of flow through of repair related deferred tax liabilities | change |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of current tax benefit from Tax Cuts and Jobs Act of 2017 to be used to reduce regulatory assets | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of current tax benefit from Tax Cuts and Jobs Act of 2017 to be returned to customers via bill credits | 20.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WE | MichiganPublicServiceCommissionMPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Electric Customers Served in Michigan | customer |  |  |  |  |  |  |  |  |  |  |  |  | 1 | 1 |  |
WG | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  | 10.30% |  |  |  |  |  |  |  |  |
WPS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1.9 | 1.6 | $ 8.1
WPS | Forward Wind Energy Center |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of utilities, along with WPS, that entered in an agreement to purchase Forward Wind Energy Center | utility |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |
Number of wind turbines at Forward Wind Energy Center | wind_turbines |  |  |  |  |  | 86 |  |  |  |  |  |  |  |  |  |
Capacity of Forward Wind Energy Center | MW |  |  |  |  |  | 138 |  |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | Two Creeks Solar Farm [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS individual ownership interest | MW | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | Badger Hollow and Two Creeks Solar Farms [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Solar Projects in WI that WPS Filed with the PSCW to Acquire an Interest In | solar_projects | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS Total Ownership Capacity in Badger Hollow and Two Creeks | MW | 200 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS Total Share of Cost of Badger Hollow and Two Creeks | $ 260.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | Badger Hollow Solar Farm [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS individual ownership interest | MW | 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |
Authorized revenue requirement for the ReACT project |  |  |  |  |  |  | $ 275.0 |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | 51.0 |  |
Estimated cost of the ReACT project, excluding AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 342.0 |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of current tax benefit from Tax Cuts and Jobs Act of 2017 to be used to reduce regulatory assets | 40.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of current tax benefit from Tax Cuts and Jobs Act of 2017 to be returned to customers via bill credits | 60.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 51.00% |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized revenue requirement for the ReACT project |  |  |  |  |  |  |  |  |  |  | $ 275.0 | $ 275.0 |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  | $ (7.9) |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  | (0.80%) |  |  |  |
Percent fuel costs can vary from the rate case approved costs before deferral is required |  |  |  |  |  |  |  |  |  |  |  | 2.00% |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  | $ (6.2) |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  | (2.10%) |  |  |  |
WE, WG, and WPS | Public Service Commission of Wisconsin (PSCW) | Natural gas storage facilities in Michigan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of natural gas storage needs provided by the facilities |  |  |  |  |  |  |  | 33.33% |  |  |  |  |  |  |  |
WE, WG, and WPS | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ActualROEInExcessOfAuthorizedAmount |  |  |  |  |  |  | 0.50% |  |  |  |  |  |  |  |  |
Number of utilities with earnings sharing mechanism | utility |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |
Percentage of first 50 basis points of additional utility earnings shared with customers |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |
WE, WG, and WPS | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of current tax benefit from Tax Cuts and Jobs Act of 2017 to be returned to customers via bill credits | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Michigan Gas Utilities Corporation and Upper Michigan Energy Resources Corporation [Member] | MichiganPublicServiceCommissionMPSC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of filings required related to the Tax Cuts and Jobs Act of 2018 | Filings |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |
PGL | Illinois Commerce Commission (ICC) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of rate base reduction as a result of a settlement |  |  | $ 5.4 |  |  |  |  |  |  |  |  |  |  |  |  |
Amount to be refunded to ratepayers as a result of a settlement |  |  | $ 4.7 |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of assurance that costs incurred under QIP rider are recoverable | Assurance |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  |
MERC | Minnesota Public Utilities Commission (MPUC) | 2018 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 9.70% |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  | $ 3.1 |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  | 1.26% |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  | 50.90% |  |  |
Interim rate increase |  | $ 7.0 |  |  | $ 9.5 |  |  |  |  |  |  |  |  |  |  |
Interim rate increase (as a percent) |  | 2.81% |  |  | 3.78% |  |  |  |  |  |  |  |  |  |  |
Interim Rate Reduction |  | $ 2.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim rates return on equity (as a percent) |  | 9.11% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim rates common equity component average (as a percent) |  | 50.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |
MERC | Minnesota Public Utilities Commission (MPUC) | 2016 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  | 9.11% |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  | $ 6.8 |  |  |  |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  | 3.00% |  |  |  |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  | 50.32% |  |  |  |  |  |  |
Number of years decoupling mechanism authorized for use |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |
Interim rates refunded to customers |  |  |  |  |  |  |  |  |  |  |  |  | $ 4.1 | $ 4.1 |  |
MGU | Michigan Public Service Commission (MPSC) | 2016 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 9.90% |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  | $ 3.4 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  | 2.40% |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 52.00% |  |  |  |
UMERC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.4 | $ 0.1 |
Term of electric power purchase agreement (in years) |  |  |  |  |  |  |  |  |  | 20 years |  |  |  |  |  |
Capacity of natural gas-fired generation facility (in megawatts) | MW |  |  |  |  |  | 180 |  |  |  | 180 |  |  |  |  |  |
Estimated cost of constructing power plant |  |  |  |  |  |  |  |  |  |  |  |  |  | 266.0 |  |
Estimated cost of constructing a power plant, including AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 277.0 |  |
Portion of the power plant costs recoverable from Tilden Mining Company (as a percent) |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |
Portion of the power plant costs recoverable from utility customers (as a percent) |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |
Utility operations | Tax Cuts and Jobs Act of 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in deferred income taxes from tax legislation |  |  |  | $ 2,450.0 |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The authorized revenue requirement for ReACT that was used to calculate the ReACT deferral. + References No definition available. + Details
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- Definition The number of utilities, in addition to Wisconsin Public Service Corporation, that enetered into an agreement to purchase the Forward Wind Energy Center. + References No definition available. + Details
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- Definition In May 2018 WPS filed an application with the PSCW to acquire an interest in two solar projects + References No definition available. + Details
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- Definition Percentage of the company's Wisconsin natural gas storage needs provided by the natural gas storage facility. + References No definition available. + Details
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- Definition The portion (as a percent) of the costs to construct a power plant that will be recovered from the Tilden Mining Company. + References No definition available. + Details
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- Definition WPS Total Ownership Capacity in solar projects + References No definition available. + Details
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