CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Operating revenue:
Oil production	$ 184,498	$ 182,181	$ 371,423	$ 383,939
Gas production	47,832	28,146	84,654	57,003
Natural gas liquids production	11,200	9,866	20,378	23,318
Other operational income	979	952	1,786	1,842
Derivative income, net	1,368	5,416	147	4,931
Total operating revenue	245,877	226,561	478,388	471,033
Operating expenses:
Lease operating expenses	50,517	51,555	103,561	96,035
Transportation, processing and gathering expenses	8,896	5,492	14,293	9,149
Production taxes	4,091	2,358	6,180	5,736
Depreciation, depletion and amortization	87,209	87,133	162,644	171,708
Accretion expense	8,318	8,255	16,581	16,521
Salaries, general and administrative expenses	15,198	13,143	29,150	26,848
Incentive compensation expense	2,050	2,398	3,481	3,840
Other operational expenses	73	71	145	113
Total operating expenses	176,352	170,405	336,035	329,950
Income from operations	69,525	56,156	142,353	141,083
Other (income) expenses:
Interest expense	8,895	7,684	18,530	13,415
Interest income	(115)	(79)	(232)	(110)
Other income	(682)	(366)	(1,408)	(786)
Total other (income) expenses	8,098	7,239	16,890	12,519
Income before income taxes	61,427	48,917	125,463	128,564
Provision (benefit) for income taxes:
Current	(6,993)	(665)	(10,739)	569
Deferred	29,398	19,035	56,422	46,474
Total income taxes	22,405	18,370	45,683	47,043
Net income	$ 39,022	$ 30,547	$ 79,780	$ 81,521
Basic earnings per share	$ 0.78	$ 0.62	$ 1.60	$ 1.65
Diluted earnings per share	$ 0.78	$ 0.62	$ 1.60	$ 1.65
Average shares outstanding	48,687	48,303	48,653	48,279
Average shares outstanding assuming dilution	48,725	48,344	48,691	48,322