COMMITMENTS AND CONTINGENCIES (Details) $ in Millions			3 Months Ended
		Feb. 01, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Environmental liability			$ 162.0	$ 132.2
Martinez Acquisition [Member]
Loss Contingencies [Line Items]
Term of Agreement			4 years
Contingent consideration	[1]	$ 77.3
Business Combination, Contingent Consideration, Liability			$ 24.3
Contingent Consideration, Discount Rate			0.246
Contingent Consideration, Undiscounted Liability			$ 43.5
Environmental Issue [Member] | Torrance Refinery [Member]
Loss Contingencies [Line Items]
Environmental liability			119.8	121.3
Other Noncurrent Liabilities [Member]
Loss Contingencies [Line Items]
Environmental liability			$ 149.4	$ 119.9

[1] The Martinez Acquisition includes an obligation for the Company to make post-closing earn-out payments to the Seller based on certain earnings thresholds of the Martinez refinery (as set forth in the Sale and Purchase Agreement), for a period of up to four years following the acquisition closing date (the “Martinez Contingent Consideration”). The Company recorded the Martinez Contingent Consideration based on its estimated fair value of $77.3 million at the acquisition date, which was recorded within “Other long-term liabilities” within the Condensed Consolidated Balance Sheets.