INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
INCOME TAXES
Effective tax rate (as a percent)	1.50%	27.50%	(6.70%)	26.70%
Income tax benefit from investment tax credit		$ 1.3		$ 1.3
Benefit from the reversal of unrecognized tax positions due to statute expiration			$ 2.9
Income Tax Benefit, Utilization of Losses at Higher Rate, Coronavirus Aid, Relief, and Economic Security Act	$ 0.6		1.0
Interest on unrecognized tax position	0.4	$ 0.5	1.4
Income tax benefit from reversal of deferred tax liability due to intercompany debt restructure				$ 0.5
Change in valuation allowance	$ 0.2		$ 0.6