FAIR VALUE MEASUREMENTS (Measured on Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019 |
Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Defined Benefit Plan, Plan Assets, Amount | $ 21.3 | $ 10.3 |
Commodity contract [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 12 | 33.8 |
Derivative liability, effect of counter-party netting | (12) | (33.8) |
Derivative Liability | 0 | 0 |
Commodity contract [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 1.2 | 32.8 |
Commodity contract [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 10.7 | 1 |
Commodity contract [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 0.1 | 0 |
Catalyst Obligation [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, effect of counter-party netting | 0 | 0 |
Obligations, Fair Value Disclosure | 86.6 | 47.6 |
Catalyst Obligation [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | 0 |
Catalyst Obligation [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 86.6 | 47.6 |
Catalyst Obligation [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | 0 |
Contingent Consideration [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, effect of counter-party netting | 0 | |
Obligations, Fair Value Disclosure | 13.7 | |
Contingent Consideration [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | |
Contingent Consideration [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | |
Contingent Consideration [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 13.7 | |
Inventory Intermediation Agreement Obligation [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | | 1.3 |
Derivative liability, effect of counter-party netting | | 0 |
Derivative Liability | | 1.3 |
Inventory Intermediation Agreement Obligation [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | | 0 |
Inventory Intermediation Agreement Obligation [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | | 1.3 |
Inventory Intermediation Agreement Obligation [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | | 0 |
Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 256.6 | 111.8 |
Money market funds [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 256.6 | 111.8 |
Money market funds [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 0 | 0 |
Money market funds [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 0 | 0 |
Commodity contract [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 12.2 | 34 |
Derivative assets, effect of counter-party netting | (12) | (33.8) |
Derivative assets, net carrying value | 0.2 | 0.2 |
Commodity contract [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 1 | 32.5 |
Commodity contract [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 9.9 | 1.5 |
Commodity contract [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 1.3 | $ 0 |
Inventory Intermediation Agreement Obligation [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 17.8 | |
Derivative assets, effect of counter-party netting | 0 | |
Derivative assets, net carrying value | 17.8 | |
Inventory Intermediation Agreement Obligation [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 0 | |
Inventory Intermediation Agreement Obligation [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 17.8 | |
Inventory Intermediation Agreement Obligation [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | $ 0 | |