VARIABLE INTEREST ENTITIES - WEPCO ENVIRONMENTAL TRUST (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2020	Mar. 31, 2022	Dec. 31, 2021
Assets
Other current assets (restricted cash)		$ 31.8	$ 19.6
Regulatory assets		3,163.6	3,264.8
Other long-term assets (restricted cash)		54.0	51.6
Liabilities
Accounts payable		693.7	1,005.7
WEPCo Environmental Trust
Variable interest entities
Securitization of environmental control costs related to Pleasant Prairie power plant	$ 100.0
Assets
Other current assets (restricted cash)		5.6	2.4
Regulatory assets		98.2	100.7
Other long-term assets (restricted cash)		0.6	0.6
Liabilities
Current portion of long-term debt		8.8	8.8
Accounts payable		0.1	0.0
Other current liabilities (accrued interest)		0.5	0.1
Long-term debt		$ 102.8	$ 102.7