Derivative Commodity Instruments - Not Designated as Hedging Instruments on the Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on fair value of derivatives	$ 20,412	$ 107,173	$ (40,005)	$ 90,245
Gain (loss) on derivative instruments, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain on fair value of derivatives	$ 20,412	$ 107,173	$ (40,005)	$ 90,245