Other Income, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
AFUDC – Equity	$ 14.4	$ 15.2	$ 11.4
Non-service components of net periodic benefit costs	36.2	26.0	9.1
Gains (losses) from investments held in rabbi trust	21.2	(1.8)	21.5
Other, net	30.4	30.9	31.7
Other income, net	$ 102.2	$ 70.3	$ 73.7