COMMITMENTS AND CONTINGENCIES - Contingencies (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Environmental obligations	$ 41.4	$ 2.0
Less current portion	6.5	0.3
Long-term environmental obligations	34.9	$ 1.7
Hamilton Plant [Member]
Loss Contingencies [Line Items]
Environmental obligations	0.7
Ashland Works Coke Plant [Member]
Loss Contingencies [Line Items]
Environmental obligations	$ 1.4

Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable in twelve months or in the next operating cycle if longer.

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