Derivatives - Schedule of Pre-Tax Gain (Loss) Recognized in the Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commodity derivatives | Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives gain (loss)	$ (3,420)	$ (4,517)	$ (1,338)
J. Aron repurchase obligation derivative | Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives gain (loss)	23,649	436	(29,810)
Interest rate derivatives | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives gain (loss)	$ 1,309	$ 489	$ 2,729