REGULATORY ENVIRONMENT - WI 2020 AND 2021 RATES (Details) $ in Millions	1 Months Ended
	May 31, 2021 USD ($)	Nov. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) utility
WEPCo Environmental Trust | WEPCo Environmental Trust Bonds 1.578%, due 2035
Public Utilities, General Disclosures [Line Items]
Proceeds from issuance of debt	$ 118.8
Debt instrument stated interest rate percentage	1.578%
Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Number of utilities filing rate requests | utility			3
Number of utilities with earnings sharing mechanism | utility			3
Percentage of first 25 basis points of additional earnings retained by the utility			100.00%
Return on equity in excess of authorized amount (as a percent)			0.25%
Percentage of additional earnings between 25 and 75 basis points refunded to customers			50.00%
Return on equity in excess of first 25 basis points above authorized amount (as a percent)			0.50%
Percentage of earnings in excess of 75 basis points refunded to customers			100.00%
Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization period			2 years
Public Service Commission of Wisconsin (PSCW) | 2020 and 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Number of utilities filing rate requests | utility			3
Amortization period			4 years
Public Service Commission of Wisconsin (PSCW) | WE | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)			10.00%
Approved common equity component average (as a percent)			52.50%
Public Service Commission of Wisconsin (PSCW) | WE | 2020 and 2021 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Pleasant Prairie power plant's book value to be securitized		$ 100.0
Public Service Commission of Wisconsin (PSCW) | WE | 2020 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ 15.3
Approved rate increase (as a percent)			0.50%
Public Service Commission of Wisconsin (PSCW) | WE | 2020 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 65.0
Public Service Commission of Wisconsin (PSCW) | WE | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ 10.4
Approved rate increase (as a percent)			2.80%
Public Service Commission of Wisconsin (PSCW) | WE | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ (5.0)
Public Service Commission of Wisconsin (PSCW) | WE | 2020 rates | Steam rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ 1.9
Approved rate increase (as a percent)			8.60%
Public Service Commission of Wisconsin (PSCW) | WE | 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 65.0
Public Service Commission of Wisconsin (PSCW) | WE | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ (5.0)
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)			10.00%
Approved common equity component average (as a percent)			52.50%
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 and 2021 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Authorized revenue requirement for ReACT			$ 275.0
Cost of the ReACT project			$ 342.0
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 and 2021 rates | Electric rates | ReACT
Public Utilities, General Disclosures [Line Items]
Collection of ReACT regulatory asset in years			8 years
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 and 2021 rates | Electric rates | Earnings sharing mechanisms
Public Utilities, General Disclosures [Line Items]
Amortization period			2 years
Amortization of regulatory liabilities			$ 21.0
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 rates | Electric rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ 15.8
Approved rate increase (as a percent)			1.60%
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 11.0
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ 4.3
Approved rate increase (as a percent)			1.40%
Public Service Commission of Wisconsin (PSCW) | WPS | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 5.0
Public Service Commission of Wisconsin (PSCW) | WPS | 2021 rates | Electric rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			39.0
Public Service Commission of Wisconsin (PSCW) | WPS | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 5.0
Public Service Commission of Wisconsin (PSCW) | WG | 2020 and 2021 rates
Public Utilities, General Disclosures [Line Items]
Approved return on equity (as a percent)			10.20%
Approved common equity component average (as a percent)			52.50%
Public Service Commission of Wisconsin (PSCW) | WG | 2020 rates | Natural gas rates
Public Utilities, General Disclosures [Line Items]
Approved rate increase			$ (1.5)
Approved rate increase (as a percent)			(0.20%)
Public Service Commission of Wisconsin (PSCW) | WG | 2020 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 3.0
Public Service Commission of Wisconsin (PSCW) | WG | 2021 rates | Natural gas rates | Tax Cuts and Jobs Act of 2017
Public Utilities, General Disclosures [Line Items]
Amortization of regulatory liabilities			$ 3.0
Public Service Commission of Wisconsin (PSCW) | WEPCo Environmental Trust | WEPCo Environmental Trust Bonds 1.578%, due 2035
Public Utilities, General Disclosures [Line Items]
Proceeds from issuance of debt	$ 118.8
Debt instrument stated interest rate percentage	1.578%