Derivative Instruments (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss Recognized in Other Comprehensive Income	$ (1,275)	$ (3,454)	$ (1,420)	$ (1,856)
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss Recognized in Other Comprehensive Income	(595)	(1,471)	206	3,446
Oil and gas sales | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Reclassified into Income	$ 1,155	$ 4,029	$ 2,187	$ 6,401