LEASES - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Cost of goods sold before depreciation, depletion and amortization	$ 5.5	$ 5.9
Selling, general and administrative expenses	0.7	0.5
Cost of goods sold before depreciation, depletion and amortization	6.2	6.4
Depreciation, depletion and amortization	3.7	2.7
Interest expense, net	0.8	0.6
Total finance lease cost	4.5	3.3
Total lease cost	10.7	9.7
Short-term lease and variable lease costs	$ 1.7	$ 1.5