Inventory Financing Agreements (Details) barrel / d in Thousands			3 Months Ended		6 Months Ended
	May 08, 2017 USD ($)	Jun. 01, 2015 USD ($) barrel / d	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Feb. 29, 2016 USD ($) installment	Sep. 30, 2015 USD ($) payment
Supply Commitment [Line Items]
Supply and exchange agreement expenses			$ 9,139,000	$ 6,106,000	$ 18,081,000	$ 10,719,000
Supply and Offtake Agreements
Supply Commitment [Line Items]
Agreement extension term	1 year
Forward sale liability	$ 30,000,000
Barrels of crude per day provided (up to) | barrel / d		94
Handling fees			3,300,000	2,000,000	6,400,000	3,900,000
Supply and exchange agreement expenses			700,000	$ 700,000	1,500,000	$ 1,300,000
Amount of deferred payment arrangement		$ 125,000,000
Percentage of receivables and inventory for deferred payment arrangement		85.00%
Deferral arrangement fee		$ 1,300,000
Variable interest rate basis		P3M
Capacity of deferred payment arrangement			58,400,000		58,400,000		$ 59,400,000
Outstanding amount of deferred payment arrangement			40,900,000		40,900,000		43,300,000
Fee agreement receivable			$ 9,700,000		$ 9,700,000		$ 14,600,000	$ 14,600,000	$ 18,000,000
Number of fee agreement payments								18	14
Supply and Offtake Agreements | London Interbank Offered Rate (LIBOR)
Supply Commitment [Line Items]
Margin on LIBOR rate		3.75%
Deferred payment availability fee		0.75%