Variable Interest Entities - WEPCo Environmental Trust (Details) - USD ($) $ in Millions	1 Months Ended
	Nov. 30, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Other current assets (restricted cash)		$ 25.6	$ 19.6	$ 0.0
Regulatory assets		3,264.6	3,264.8
Other long-term assets (restricted cash)		127.7	51.6	$ 47.8
Liabilities
Current portion of long-term debt		808.5	91.0
Long-term debt		14,655.7	13,472.4
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)		3.0	2.4
Regulatory assets		92.4	100.7
Other long-term assets (restricted cash)		0.6	0.6
Liabilities
Current portion of long-term debt		8.9	8.8
Other current liabilities (accrued interest)		0.1	0.1
Long-term debt		$ 94.1	$ 102.7