CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Operating revenue:
Oil production	$ 186,608	$ 180,806	$ 558,031	$ 564,745
Gas production	52,728	34,003	137,382	91,006
Natural gas liquids production	16,476	11,910	36,854	35,228
Other operational income	873	678	2,659	2,520
Derivative income, net				3,119
Total operating revenue	256,685	227,397	734,926	696,618
Operating expenses:
Lease operating expenses	53,986	60,995	157,547	157,030
Transportation, processing and gathering expenses	13,081	6,762	27,374	15,911
Production taxes	5,224	1,842	11,404	7,578
Depreciation, depletion and amortization	92,853	89,274	255,497	260,982
Accretion expense	8,431	8,405	25,012	24,926
Salaries, general and administrative expenses	14,201	13,673	43,351	40,521
Incentive compensation expense	4,566	67	8,047	3,907
Other operational expenses	237	82	382	195
Derivative expense, net	1,684	1,812	1,537
Total operating expenses	194,263	182,912	530,151	511,050
Income from operations	62,422	44,485	204,775	185,568
Other (income) expenses:
Interest expense	7,922	7,692	26,452	21,107
Interest income	(1,311)	(117)	(1,543)	(227)
Other income	(782)	(443)	(2,190)	(1,229)
Total other (income) expenses	5,829	7,132	22,719	19,651
Income before income taxes	56,593	37,353	182,056	165,917
Provision (benefit) for income taxes:
Current	(88)	595	(10,827)	1,164
Deferred	20,579	13,099	77,001	59,573
Total income taxes	20,491	13,694	66,174	60,737
Net income	$ 36,102	$ 23,659	$ 115,882	$ 105,180
Basic earnings per share	$ 0.72	$ 0.48	$ 2.32	$ 2.13
Diluted earnings per share	$ 0.72	$ 0.48	$ 2.32	$ 2.13
Average shares outstanding	48,732	48,342	48,680	48,300
Average shares outstanding assuming dilution	48,776	48,384	48,720	48,343