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VARIABLE INTEREST ENTITIES - TRANSMISSION AFFILIATES (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Variable interest entities
Equity method investment	$ 2,341.4			$ 2,163.8
American Transmission Company LLC
Variable interest entities
Ownership interest (as a percent)	60.00%
Equity method investment	$ 2,245.6	$ 2,177.5	$ 2,085.1	2,054.1	$ 2,029.7	$ 1,980.8
ATC Holdco LLC
Variable interest entities
Ownership interest (as a percent)	75.00%
Equity method investment	$ 23.2	$ 22.6	$ 23.8	$ 26.7	$ 26.1	$ 25.1

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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