FAIR VALUE MEASUREMENTS (Measured on Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions | Jun. 30, 2021 | Dec. 31, 2020 |
Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Defined Benefit Plan, Plan Assets, Amount | $ 20.9 | $ 21.2 |
Commodity contract [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 46.5 | 9 |
Derivative liability, effect of counter-party netting | (32.6) | (6) |
Derivative Liability | 13.9 | 3 |
Commodity contract [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 46.5 | 2.3 |
Commodity contract [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative liability, gross carrying value | 0 | 6.7 |
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 | 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 | 106.6 | 102.5 |
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 | 106.6 | 102.5 |
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 | 0 |
Obligations, Fair Value Disclosure | 26.1 | 12.1 |
Contingent Consideration [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | 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 | 0 |
Contingent Consideration [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 26.1 | 12.1 |
Renewable Energy Credit and Emissions Obligation | | |
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 | 1,114.2 | 528.1 |
Renewable Energy Credit and Emissions Obligation | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | 0 |
Renewable Energy Credit and Emissions Obligation | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 1,114.2 | 528.1 |
Renewable Energy Credit and Emissions Obligation | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Obligations, Fair Value Disclosure | 0 | 0 |
Money market funds [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 254.7 | 411.6 |
Money market funds [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash and cash equivalents | 254.7 | 411.6 |
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 | 32.6 | 6 |
Derivative assets, effect of counter-party netting | (32.6) | (6) |
Derivative assets, net carrying value | 0 | 0 |
Commodity contract [Member] | Level 1 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 30.8 | 2.5 |
Commodity contract [Member] | Level 2 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 1.8 | 3.5 |
Commodity contract [Member] | Level 3 [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | 0 | 0 |
Inventory Intermediation Agreement Obligation [Member] | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Derivative assets, gross carrying value | (30.9) | 11.3 |
Derivative assets, effect of counter-party netting | 0 | 0 |
Derivative assets, net carrying value | (30.9) | 11.3 |
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 | 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 | (30.9) | 11.3 |
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 | $ 0 |