Consolidated Balance Sheets Parenthetical (Parentheticals) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Accounts receivable and unbilled revenues, reserves	$ 44.5	$ 49.7
Property, plant, and equipment, accumulated depreciation and amortization	$ 5,779.2	$ 5,450.3
Common stock, par value	$ 10	$ 10
Common stock, shares authorized	65,000,000	65,000,000
Common stock, shares outstanding	33,289,327	33,289,327
Regulatory assets (December 31, 2023 and December 31, 2022 include $85.9 and $92.4, respectively, related to WEPCo Environmental Trust)	$ 2,860.7	$ 2,817.5
Current portion of long-term debt (December 31, 2023 and December 31, 2022 include $9.0 and $8.9, respectively, related to WEPCo Environmental Trust)	309.0	8.9
Long-term debt (December 31, 2023 and December 31, 2022 include $85.3 and $94.1, respectively, related to WEPCo Environmental Trust)	3,045.4	3,351.5
WEPCo Environmental Trust
Regulatory assets (December 31, 2023 and December 31, 2022 include $85.9 and $92.4, respectively, related to WEPCo Environmental Trust)	85.9	92.4
Current portion of long-term debt (December 31, 2023 and December 31, 2022 include $9.0 and $8.9, respectively, related to WEPCo Environmental Trust)	9.0	8.9
Long-term debt (December 31, 2023 and December 31, 2022 include $85.3 and $94.1, respectively, related to WEPCo Environmental Trust)	$ 85.3	$ 94.1