CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating revenue:
Oil production	$ 186,925	$ 201,758
Gas production	36,822	28,857
Natural gas liquids production	9,178	13,452
Other operational income	807	890
Total operating revenue	233,732	244,957
Operating expenses:
Lease operating expenses	53,044	44,480
Transportation, processing and gathering expenses	5,397	3,657
Production taxes	2,089	3,378
Depreciation, depletion and amortization	75,435	84,575
Accretion expense	8,263	8,266
Salaries, general and administrative expenses	13,952	13,705
Incentive compensation expense	1,431	1,442
Derivative expense, net	1,221	485
Other operational expenses	72	42
Total operating expenses	160,904	160,030
Income from operations	72,828	84,927
Other (income) expenses:
Interest expense	9,635	5,731
Interest income	(117)	(31)
Other income	(726)	(420)
Total other (income) expenses	8,792	5,280
Income (loss) before taxes	64,036	79,647
Provision (benefit) for income taxes:
Current	(3,746)	1,234
Deferred	27,024	27,439
Total income taxes	23,278	28,673
Net income	$ 40,758	$ 50,974
Basic earnings per share	$ 0.82	$ 1.04
Diluted earnings per share	$ 0.82	$ 1.04
Average shares outstanding	48,619	48,254
Average shares outstanding assuming dilution	48,657	48,299