REGULATORY ENVIRONMENT (Details) $ in Millions	1 Months Ended					6 Months Ended
	Jun. 30, 2019 USD ($) Assurance	Mar. 31, 2019 USD ($) company	Dec. 31, 2018 USD ($)	Feb. 28, 2018 Filings	Sep. 30, 2017 USD ($) utility	Jun. 30, 2019 USD ($) Assurance	Aug. 01, 2019 USD ($) MW	May 31, 2018 USD ($) solar_projects MW
WE | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Electric rates
Regulatory environment
Requested rate increase		$ 83.0
Requested rate increase (as a percent)		2.90%
WE | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Natural gas rates
Regulatory environment
Requested rate increase		$ 15.0
Requested rate increase (as a percent)		3.90%
WE | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Steam rates
Regulatory environment
Requested rate increase		$ 1.0
Requested rate increase (as a percent)		4.50%
WE | Public Service Commission of Wisconsin (PSCW) | 2021 rates | Electric rates
Regulatory environment
Requested rate increase		$ 83.0
Requested rate increase (as a percent)		2.90%
WE | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates
Regulatory environment
Requested return on equity (as a percent)		10.35%
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						$ 0.0
WG | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Natural gas rates
Regulatory environment
Requested rate increase		$ 11.0
Requested rate increase (as a percent)		1.80%
WG | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates
Regulatory environment
Requested return on equity (as a percent)		10.30%
WG | Public Service Commission of Wisconsin (PSCW) | 2018 and 2019 rates
Regulatory environment
Approved return on equity (as a percent)					10.30%
WPS | Public Service Commission of Wisconsin (PSCW) | Badger hollow solar farm and two creeks solar project
Regulatory environment
Number of solar projects for which approval has been requested | solar_projects								2
Total output of two solar projects owned by WPS (in megawatts) | MW								200
WPS share of cost for certain solar projects								$ 260.0
WPS | Public Service Commission of Wisconsin (PSCW) | Two creeks solar project
Regulatory environment
Solar project output owned by WPS (in megawatts) | MW								100
WPS | Public Service Commission of Wisconsin (PSCW) | Badger hollow I solar farm
Regulatory environment
Solar project output owned by WPS (in megawatts) | MW								100
WPS | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Electric rates
Regulatory environment
Requested rate increase		$ 49.0
Requested rate increase (as a percent)		4.90%
WPS | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Natural gas rates
Regulatory environment
Requested rate increase		$ 7.0
Requested rate increase (as a percent)		2.40%
WPS | Public Service Commission of Wisconsin (PSCW) | 2021 rates | Electric rates
Regulatory environment
Requested rate increase		$ 49.0
Requested rate increase (as a percent)		4.90%
WPS | Public Service Commission of Wisconsin (PSCW) | 2021 rates | Natural gas rates
Regulatory environment
Requested rate increase		$ 7.0
Requested rate increase (as a percent)		2.40%
WPS | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates
Regulatory environment
Requested return on equity (as a percent)		10.35%
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
WE, WG, and WPS | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates
Regulatory environment
Number of companies filing rate increase request | company		3
Requested common equity component average (as a percent)		52.00%
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 | Illinois Commerce Commission (ICC)
Regulatory environment
Rate base reduction from settlement of 2015 reconciliation	$ 7.0					$ 7.0
Refund to ratepayers from settlement of 2015 reconciliation	$ 7.3
Amount of assurance that PGL's QIP rider costs will be recoverable | Assurance	0					0
MERC | Minnesota Public Utilities Commission (MPUC) | 2018 rates | Natural gas rates
Regulatory environment
Change in regulatory liabilities from tax legislation						$ 7.6
Approved return on equity (as a percent)			9.70%
Approved rate increase			$ 3.1
Approved rate increase (as a percent)			1.26%
Approved common equity component average (as a percent)			50.90%
MGU and UMERC | Michigan Public Service Commission (MPSC)
Regulatory environment
Number of filings required related to the Tax Cuts and Jobs Act of 2017 | Filings				3
Tax Cuts and Jobs Act of 2017 | WE | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates | Electric rates
Regulatory environment
Change in regulatory liabilities from tax legislation		$ 111.0
Tax Cuts and Jobs Act of 2017 | WPS | Public Service Commission of Wisconsin (PSCW) | 2020 rates | Natural gas rates
Regulatory environment
Change in regulatory liabilities from tax legislation		7.0
Tax Cuts and Jobs Act of 2017 | WPS | Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates | Electric rates
Regulatory environment
Change in regulatory liabilities from tax legislation		$ 40.0
Subsequent event | WE | Public Service Commission of Wisconsin (PSCW) | Badger hollow II solar farm
Regulatory environment
Solar project output that approval was requested for from the PSCW (in megawatts) | MW							100
WE share of cost of badger hollow II							$ 130.0