Derivative Instruments (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive income	$ 3,564,000	$ (3,654,000)	$ 3,564,000	$ (3,654,000)	$ 5,420,000	$ (4,514,000)	$ (1,096,000)
Realization of gain, net of taxes			3,600,000
Gas hedges
Derivatives, Fair Value [Line Items]
Gain or loss recognized in oil and gas contracts	4,181,000	(2,170,000)	6,505,000	(5,139,000)
Oil hedges
Derivatives, Fair Value [Line Items]
Gain or loss recognized in oil and gas contracts	(288,000)	(672,000)	(261,000)	(1,106,000)
Ngl hedges
Derivatives, Fair Value [Line Items]
Gain or loss recognized in oil and gas contracts	$ 136,000	$ 0	$ 157,000	$ 0