Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Non-service components of net periodic benefit costs	Other income, net	Other income, net	Other income, net
Non-service components of net periodic benefit costs	$ 97.7	$ 104.4	$ 72.2
AFUDC - Equity	59.1	29.4	18.0
Gains (losses) from investments held in rabbi trust	13.7	(12.6)	18.6
Other, net	8.3	(1.7)	4.5
Other income, net	177.7	128.8	133.2
Equity method investments excluding transmission affiliates
Earnings (Loss) from Equity Method Investment	$ (1.1)	$ 9.3	$ 19.9