FAIR VALUE MEASUREMENTS (Fair Value and Carrying Value of Debt) (Details) - USD ($) $ in Millions		Jun. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Gross		$ 1,468.8	$ 1,470.1
Unamortized premium		0.0	0.0
Less - Unamortized deferred financing costs		(27.3)	(35.2)
Long-term debt, Carrying value		1,441.5	1,434.9
Long-term debt, Fair value		1,415.2	1,363.7
Long-term debt, excluding current maturities, Fair value		1,415.2	1,363.7
2028 Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	[1]	801.6	801.6
Long-term debt, Fair value	[1]	747.9	703.7
2025 Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	[1]	664.5	664.5
Long-term debt, Fair value	[1]	664.6	656.0
Catalyst financing arrangements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	[2]	2.7	4.0
Long-term debt, Fair value	[2]	$ 2.7	$ 4.0

[1] The estimated fair value, categorized as a Level 2 measurement, was calculated based on the present value of future expected payments utilizing implied current market interest rates based on quoted prices of the outstanding senior notes.

[2] Catalyst financing arrangements are valued using a market approach based upon commodity prices for similar instruments quoted in active markets and are categorized as a Level 2 measurement. The Company has elected the fair value option for accounting for its catalyst repurchase obligations as the Company’s liability is directly impacted by the change in fair value of the underlying catalyst.