Inventory Financing Agreements - Supply and Offtake Agreements (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Dec. 05, 2018 USD ($) mbpd	Jun. 27, 2018	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Feb. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 03, 2019 USD ($)	Mar. 01, 2019 USD ($)	Jun. 01, 2018 USD ($)	Jun. 01, 2015 USD ($)
Supply Commitment [Line Items]
Supply and exchange agreement expenses			$ 16,414	$ 20,278	$ 35,088	$ 38,988
Supply and Offtake Agreements
Supply Commitment [Line Items]
Agreement extension term					1 year
Deferred payment arrangement, aggregate marginal increase	$ 2,500								$ 2,500	$ 2,500
Barrels of crude per day provided (up to) (in mbpd) | mbpd	150
Supply and exchange agreement expenses			800	1,400	$ 2,100	3,100
Amount of deferred payment arrangement	$ 165,000
Percentage of receivables and inventory for deferred payment arrangement		85.00%
Deferral arrangement fee												$ 1,300
Capacity of deferred payment arrangement			75,600		75,600			$ 155,500
Outstanding amount of deferred payment arrangement			47,200		47,200			97,500
Fee agreement receivable (payable)			1,100		1,100		$ 800	$ 500			$ 2,200
Supply and Offtake Agreements | London Interbank Offered Rate (LIBOR)
Supply Commitment [Line Items]
Margin on LIBOR rate	3.50%
Deferred payment availability fee	0.75%
Supply and Offtake Agreements | Inventory Intermediation
Supply Commitment [Line Items]
Inventory intermediation fee received			$ 200
Handling fees				$ 10,200	$ 6,700	$ 15,600