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Regulatory Environment (Details) $ in Millions | 1 Months Ended | 12 Months Ended
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Feb. 28, 2018 USD ($) | Dec. 31, 2017 USD ($) Assurance | Nov. 30, 2017 USD ($) | Oct. 31, 2017 USD ($) wind_turbines utility MW | Sep. 30, 2017 USD ($) utility | Jan. 31, 2017 | Oct. 31, 2016 USD ($) | Aug. 31, 2016 MW | Mar. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Jun. 30, 2015 | Apr. 30, 2015 USD ($) | Feb. 28, 2015 USD ($) | Jan. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Oct. 31, 2014 USD ($) | Dec. 31, 2017 USD ($) Assurance | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
AFUDC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4.9 | $ 10.9 | $ 8.6
Percent fuel costs can vary from the rate case approved costs before deferral is required |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  | 10.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 26.6 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.90% |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.0 |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Steam rates | Downtown Milwaukee (Valley) steam customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.0 |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Steam rates | Milwaukee County steam customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.0 |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.20% |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 51.00% |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Refund related to prior fuel costs and the remainder of the proceeds of a Treasury Grant |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 26.6 |  |  |  |
Percent fuel costs can vary from the rate case approved costs before deferral is required |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% |  |  |  |
SSR revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 90.7 |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Electric rates | Non-fuel costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2.7 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.10% |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Electric rates | Fuel costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (13.9) |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (0.50%) |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (10.7) |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (2.40%) |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Steam rates | Downtown Milwaukee (Valley) steam customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.5 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% |  |  |  |
WE | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Steam rates | Milwaukee County steam customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1.2 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.30% |  |  |  |
WG | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  | 10.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |
WG | Public Service Commission of Wisconsin (PSCW) | 2016 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 21.4 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.20% |  |  |  |
WG | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.30% |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 17.1 |  |  |  |
Approved rate increase (decrease), percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.60% |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 49.50% |  |  |  |
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 |  |  |  | 129 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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) | 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%) |  |  |  |  |  |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2015 Rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.20% |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.28% |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 24.6 |  |  |  |
Percent fuel costs can vary from the rate case approved costs before deferral is required |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% |  |  |  |
Increase in cost of fuel for electric generation |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 42.0 |  |  |  |
Year-over-year positive (negative) change in decoupling refunded to or collected from customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.0 |  |  |  |
WPS | Public Service Commission of Wisconsin (PSCW) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (15.4) |  |  |  |
Year-over-year positive (negative) change in decoupling refunded to or collected from customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (16.0) |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of utilities with earnings sharing mechanism | utility |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of first 50 basis points of additional utility earnings shared with customers |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Return on equity in excess of authorized amount (as a percent) |  |  |  |  | 0.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |
PGL and NSG | Illinois Commerce Commission (ICC) | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of base rate freeze |  |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |
PGL | Illinois Commerce Commission (ICC) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of assurance that costs incurred under QIP rider are recoverable | Assurance |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |
PGL | Illinois Commerce Commission (ICC) | Subsequent event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PGL | Illinois Commerce Commission (ICC) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.05% |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 74.8 |  |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.33% |  |  |  |  |
Amended approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  | $ 71.1 |  |  |  |  |  |
NSG | Illinois Commerce Commission (ICC) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.05% |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3.7 |  |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.48% |  |  |  |  |
Amended approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  | $ 3.5 |  |  |  |  |  |
MERC | Minnesota Public Utilities Commission (MPUC) | 2018 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase |  |  |  | $ 12.6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested rate increase (as a percent) |  |  |  | 5.05% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested return on equity (as a percent) |  |  |  | 10.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Requested common equity component average (as a percent) |  |  |  | 50.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim rate increase |  |  | $ 9.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim rate increase (as a percent) |  |  | 3.78% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 |  |
MERC | Minnesota Public Utilities Commission (MPUC) | 2015 Rates | Natural gas rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.35% |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7.6 |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.31% |  |  |
Interim rates refunded to customers |  |  |  |  |  |  |  |  |  | $ 4.7 |  |  |  |  |  |  |  |  | $ 4.7
Annual cap for decoupling mechanism (as a percent of rate case approved distribution revenues) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
UMERC | Michigan Public Service Commission (MPSC) | 2015 Rates | Electric rates |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Approved return on equity (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 10.20% |  |  |  |  |  |  |
Approved rate increase (decrease) |  |  |  |  |  |  |  |  |  |  |  | $ 4.0 |  |  |  |  |  |  |
Approved common equity component average (as a percent) |  |  |  |  |  |  |  |  |  |  |  | 50.48% |  |  |  |  |  |  |
Period of rate implementation |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |
Utility operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory environment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in deferred income taxes from tax legislation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,450.0 |  |
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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