Inventory Financing Agreements - Supply and Offtake Agreements (Details) $ in Millions						12 Months Ended
	Feb. 01, 2020 USD ($) settlement_payment	Dec. 05, 2018 mbpd	Jun. 27, 2018 USD ($)	Jun. 26, 2018 USD ($)	Jun. 01, 2015 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 03, 2019 USD ($)	Mar. 01, 2019 USD ($)	Dec. 19, 2018 USD ($)	Jun. 01, 2018 USD ($)	Dec. 01, 2016 USD ($) installment
London Interbank Offered Rate (LIBOR)
Basis spread on variable rate						3.25%
Supply and Offtake Agreements
Commitment period					1 year
Amount of deferred payment arrangement			$ 165.0	$ 125.0
Percentage of receivables and inventory for deferred payment			85.00%	85.00%
Purchase and supply commitment, deferred payment arrangement, aggregate marginal increase								$ 2.5	$ 2.5	$ 2.5
Barrels of crude per day provided by J. Aron | mbpd		150
Deferral arrangement fee					$ 1.3
Current borrowing capacity						$ 80.1	$ 155.5
Outstanding amount of deferred payment arrangement						78.6	97.5
Fee agreement receivable	$ 0.8					$ 0.5	$ 0.5				$ 2.2	$ 14.6
Number of fee agreement payments | installment												18
Number of Settlement Payments | settlement_payment	15
Supply and Offtake Agreements | London Interbank Offered Rate (LIBOR)
Basis spread on variable rate		3.50%
Deferred payment availability fee		0.75%