Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period	$ (4,514)	$ (3,389)	$ (1,096)	$ 521
Change in fair value of derivatives	(1,982)	4,769	(8,803)	406
Income tax effect	0	(840)	0	183
Other comprehensive loss before reclassifications	(1,982)	3,929	(8,803)	589
Oil and gas sales	2,842	878	6,245	491
Income tax effect	0	0	0	(183)
Amounts reclassified from accumulated other comprehensive income (loss)	2,842	878	6,245	308
Net other comprehensive loss	860	4,807	(2,558)	897
Balance, end of period	(3,654)	1,418	(3,654)	1,418
Gains and Losses on Cash Flow Hedges
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period	(2,834)	(2,128)	(688)	521
Change in fair value of derivatives	(1,982)	4,769	(8,803)	406
Income tax effect	737	(1,774)	3,275	183
Other comprehensive loss before reclassifications	(1,245)	2,995	(5,528)	589
Oil and gas sales	2,842	878	6,245	491
Income tax effect	(1,057)	(327)	(2,323)	(183)
Amounts reclassified from accumulated other comprehensive income (loss)	1,785	551	3,922	308
Net other comprehensive loss	540	3,546	(1,606)	897
Balance, end of period	(2,294)	1,418	(2,294)	1,418
Change in Valuation Allowance
Accumulated other Comprehensive Income [Roll Forward]
Balance, beginning of period	(1,680)	(1,261)	(408)	0
Change in fair value of derivatives		0		0
Income tax effect	(737)	934	(3,275)	0
Other comprehensive loss before reclassifications	(737)	934	(3,275)	0
Oil and gas sales		0		0
Income tax effect	1,057	327	2,323	0
Amounts reclassified from accumulated other comprehensive income (loss)	1,057	327	2,323	0
Net other comprehensive loss	320	1,261	(952)	0
Balance, end of period	$ (1,360)	$ 0	$ (1,360)	$ 0