Derivatives - Schedule of Pre-Tax Gain (Loss) Recognized in the Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Commodity derivatives | Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Cost of revenues	$ (6,367)	$ (6,855)
J. Aron repurchase obligation derivative | Cost of revenues
Derivative Instruments, Gain (Loss) [Line Items]
Cost of revenues	10,607	(22,976)
J. Aron repurchase obligation derivative | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Cost of revenues	$ 110	$ (756)