Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period		$ (4,514)	$ 5,420	$ (1,096)
Change in fair value of derivatives		(1,982)		(8,803)
Income tax effect		0		0
Net of tax		(1,982)		(8,803)
Oil and gas sales		2,842		6,245
Income tax effect		0		0
Net of tax		2,842		6,245
Net other comprehensive income (loss)		860		(2,558)
Balance, end of period	$ 3,564	(3,654)	3,564	(3,654)
Gains and Losses on Cash Flow Hedges
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period	7,018	(2,834)	5,420	(688)
Change in fair value of derivatives	(1,471)	(1,982)	3,446	(8,803)
Income tax effect	547	737	(1,282)	3,275
Net of tax	(924)	(1,245)	2,164	(5,528)
Oil and gas sales	(4,029)	2,842	(6,401)	6,245
Income tax effect	1,499	(1,057)	2,381	(2,323)
Net of tax	(2,530)	1,785	(4,020)	3,922
Net other comprehensive income (loss)	(3,454)	540	(1,856)	(1,606)
Balance, end of period	$ 3,564	(2,294)	$ 3,564	(2,294)
Change in Valuation Allowance
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period		(1,680)		(408)
Change in fair value of derivatives		0		0
Income tax effect		(737)		(3,275)
Net of tax		(737)		(3,275)
Oil and gas sales		0		0
Income tax effect		1,057		2,323
Net of tax		1,057		2,323
Net other comprehensive income (loss)		320		(952)
Balance, end of period		$ (1,360)		$ (1,360)