INCOME TAXES - SUMMARY OF INCOME TAX EXPENSE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Provision for income taxes
Current tax expense (benefit)	$ 8.7	$ (18.3)	$ 49.8
Deferred income taxes, net	66.3	51.1	5.1
Investment tax credit, net	(2.8)	(1.6)	(0.4)
Total income tax expense	$ 72.2	$ 31.2	$ 54.5