Derivative Commodity Instruments - Not Designated as Hedging Instruments on the Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Loss on derivative instruments, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) recognized in income on derivatives	$ (65,872)	$ (50,964)	$ (60,417)	$ (16,928)