OTHER INCOME, NET (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Income and Expenses [Abstract]
AFUDC - Equity	$ 4.6	$ 4.1	$ 19.5
Non-service credit components of net periodic benefit costs	16.7	11.8	10.5
Earnings from equity method investments	0.8	1.1	9.5
Other, net	15.5	6.7	1.8
Other income, net	$ 37.6	$ 23.7	$ 41.3