Derivatives - Schedule of Pre-Tax Gain (Loss) Recognized in the Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Commodity derivatives | Cost of revenues (excluding depreciation)
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	$ 3,657	$ (3,028)	$ 26	$ (3,117)
J. Aron repurchase obligation derivative | Cost of revenues (excluding depreciation)
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	(24,041)	(8,300)	(4,995)	(20,356)
Interest rate derivatives | Interest expense and financing costs, net
Derivative Instruments, Gain (Loss) [Line Items]
Pre-tax gains (losses)	$ 148	$ 1,204	$ (477)	$ (1,098)