Derivatives - Schedule of Pre-Tax Gain (Loss) Recognized in the Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Commodity derivatives | Cost of revenues (excluding depreciation)
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	$ 2,736	$ 7,660	$ (3,631)	$ (89)
J. Aron repurchase obligation derivative | Cost of revenues (excluding depreciation)
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	8,439	10,920	19,046	(12,056)
Interest rate derivatives | Interest expense and financing costs, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	$ (735)	$ (1,579)	$ (625)	$ (2,302)