CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Accounts receivable and unbilled revenues, reserves	$ 178.7	$ 199.3
Property, plant, and equipment, accumulated depreciation and amortization	$ 10,717.0	$ 10,383.8
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	325,000,000	325,000,000
Common stock, shares outstanding	315,434,531	315,434,531
Regulatory assets (June 30, 2023 and December 31, 2022 include $89.5 and $92.4, respectively, related to WEPCo Environmental Trust)	$ 3,238.9	$ 3,264.6
WEPCo Environmental Trust
Regulatory assets (June 30, 2023 and December 31, 2022 include $89.5 and $92.4, respectively, related to WEPCo Environmental Trust)	89.5	92.4
Current portion of long-term debt (June 30, 2023 and December 31, 2022 include $9.0 and $8.9, respectively, related to WEPCo Environmental Trust)	9.0	8.9
Long-term debt (June 30, 2023 and December 31, 2022 include $89.7 and $94.1, respectively, related to WEPCo Environmental Trust)	$ 89.7	$ 94.1