FAIR VALUE MEASUREMENTS (Fair Value and Carrying Value of Debt) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2018 USD ($) lease	Jun. 30, 2019 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair value		$ 1,233.7	$ 1,343.1
Long-term Debt, Gross		1,290.9	1,288.9
Current portion of long-term debt	[1]	(2.4)	(1.3)
Long-Term Debt And Capital Lease Obligations, Current, Fair Value Disclosure	[1]	(2.4)	(1.3)
Unamortized Debt Issuance Expense		$ (30.5)	(27.4)
Number Of Platinum Leases Entered Into During Period | lease		2
Long-term debt		$ 1,258.0	1,260.2
Long-term debt, excluding current maturities, Fair value		1,231.3	1,341.8
2023 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Carrying value	[2]	500.0	500.0
Long-term debt, Fair value	[2]	479.4	519.6
2025 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Carrying value	[2]	725.0	725.0
Long-term debt, Fair value	[2]	688.4	759.6
Catalyst lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Carrying value	[1]	44.3
Long-term debt, Fair value	[1]	44.3	45.8
PBF Rail Logistics Company LLC [Member] | Notes Payable to Banks [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Carrying value	[3]	21.6	18.1
Long-term debt, Fair value	[3]	$ 21.6	18.1
Catalyst lease [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Capital Lease Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Carrying value	[1]		$ 45.8
2025 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, interest rate			7.25%
2023 Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, interest rate			7.00%

[1] Catalyst leases 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 lease repurchase obligations as the Company’s liability is directly impacted by the change in fair value of the underlying catalyst. During 2018, Toledo Refining and Chalmette Refining entered into two platinum bridge leases which were settled in April 2019 and were not renewed. During 2018 Delaware City Refining entered into a new platinum bridge lease, which will expire in the third quarter of 2019. This lease is payable at maturity and is not anticipated to be renewed. The total outstanding balance related to these bridge leases as of June 30, 2019 and December 31, 2018 was $1.3 million and $2.4 million, respectively, and is included in Current debt in the Company’s Condensed Consolidated Balance Sheets.

[2] 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 7.00% senior notes due 2023 and the 7.25% senior notes due 2025 (collectively, the “Senior Notes”).

[3] 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.