Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Investment in Transmission Affiliates - ATC Return on Equity (Details) - ATC $ in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Oct. 31, 2024	Aug. 31, 2022	Dec. 31, 2024 USD ($) numberOfComplaints	Sep. 30, 2022 USD ($)	Dec. 31, 2024 USD ($) numberOfComplaints	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Allowed return on equity for American Transmission Company LLC
Number of complaints filed \| numberOfComplaints			2		2
Earnings (loss) from equity method investment					$ 205.4	$ 175.1	$ 192.6
Opinion issued by United States Court of Appeals for the District of Columbia Circuit in August 2022
Allowed return on equity for American Transmission Company LLC
Assumed return on equity (as a percent)		9.88%
Earnings (loss) from equity method investment				$ 39.1
Order issued by the Federal Energy Regulatory Commission in October 2024
Allowed return on equity for American Transmission Company LLC
Approved return on equity (as a percent)	9.98%
Earnings (loss) from equity method investment			$ 20.1