FAIR VALUE MEASUREMENTS (Fair Value and Carrying Value of Debt) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018	Dec. 22, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Gross		$ 1,287.1	$ 1,290.9
Less - Current debt (c)		0.0	(2.4)
Unamortized Debt Issuance Expense		(24.3)	(30.5)
Long-term debt		1,262.8	1,258.0
Long-term Debt, Fair Value		1,358.3	1,233.7
Less - Current maturities, Fair value	[1]	0.0	(2.4)
Long-term debt, Fair value		1,358.3	1,231.3
2025 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt		725.0	725.0
Long-term Debt, Fair Value	[2]	776.5	688.4
2023 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt		500.0	500.0
Long-term Debt, Fair Value	[2],[3]	519.7	479.4
Catalyst Obligation [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt			44.3
Long-term Debt, Fair Value	[1]	47.6	44.3
PBF Rail Logistics Company LLC [Member] | PBF Rail Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt		14.5	21.6	$ 35.0
Long-term Debt, Fair Value	[4]	$ 14.5	$ 21.6

[1] (c) 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.

[2] (a) 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 Senior Notes.

[3] (d) As disclosed in “Note 7 - Credit Facilities and Debt”, these notes became unsecured following the Collateral Fall-Away Event on May 30, 2017.

[4] (b) The estimated fair value approximates carrying value, categorized as a Level 2 measurement, as these borrowings bear interest based upon short-term floating market interest rates.