Derivative Instruments (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income	$ 245	$ (10)	$ (1,175)	$ (1,866)
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Other Comprehensive Income	101	4,077	307	7,523
Oil and gas sales | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Reclassified into Income	$ (144)	$ 4,093	$ 2,043	$ 10,494