CONDENSED CONSOLIDATED BALANCE SHEETS (PARENTHETICALS) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Accounts receivable and unbilled revenues, reserves	$ 37.7	$ 39.7
Property, plant, and equipment, accumulated depreciation and amortization	$ 6,542.5	$ 6,373.9
Common stock, par value (in dollars per share)	$ 10	$ 10
Common stock, shares authorized	65,000,000	65,000,000
Common Stock, Shares, Issued	33,289,327	33,289,327
Common stock, shares outstanding	33,289,327	33,289,327
Regulatory assets (June 30, 2026 and December 31, 2025 include $63.6 and $67.5, respectively, related to WEPCo Environmental Trust)	$ 2,948.2	$ 2,941.0
Long-term debt (June 30, 2026 and December 31, 2025 include $62.8 and $67.4, respectively, related to WEPCo Environmental Trust)	5,602.1	4,516.0
Current portion of long-term debt (June 30, 2026 and December 31, 2025 include $9.4 and $9.3, respectively, related to WEPCo Environmental Trust)	9.4	9.3
WEPCo Environmental Trust
Regulatory assets (June 30, 2026 and December 31, 2025 include $63.6 and $67.5, respectively, related to WEPCo Environmental Trust)	63.6	67.5
Long-term debt (June 30, 2026 and December 31, 2025 include $62.8 and $67.4, respectively, related to WEPCo Environmental Trust)	62.8	67.4
Current portion of long-term debt (June 30, 2026 and December 31, 2025 include $9.4 and $9.3, respectively, related to WEPCo Environmental Trust)	$ 9.4	$ 9.3

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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