CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended											12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating revenue:
Oil production												$ 516,104	$ 715,104	$ 761,304
Natural gas production												166,494	190,580	134,739
Natural gas liquids production												85,642	60,687	48,498
Other operational income												7,951	7,808	3,520
Derivative income, net												19,351		3,428
Total operating revenue	184,780		183,213		207,046	223,830	239,253		256,685	245,877	233,732	795,542	974,179	951,489
Operating expenses:
Lease operating expenses												176,495	201,153	215,003
Transportation, processing and gathering expenses												64,951	42,172	21,782
Production taxes												12,151	15,029	10,015
Depreciation, depletion and amortization												340,006	350,574	344,365
Write-down of oil and gas properties	304,062		47,130									351,192
Accretion expense												28,411	33,575	33,331
Salaries, general and administrative expenses												66,451	59,524	54,648
Franchise tax settlement							12,590						12,590
Incentive compensation expense												10,361	15,340	8,113
Other operational expenses												862	151	267
Derivative expense, net													2,090
Total operating expenses												1,050,880	732,198	687,524
Income (loss) from operations	(286,147)	[1]	(34,356)	[2]	16,613	48,552	37,206	[3]	62,422	69,525	72,828	(255,338)	241,981	263,965
Other (income) expenses:
Interest expense												38,855	32,837	30,375
Interest income												(574)	(1,695)	(600)
Other income												(2,332)	(2,799)	(1,805)
Other expense												274
Loss on early extinguishment of debt							27,279						27,279	1,972
Total other (income) expenses												36,223	55,622	29,942
Income (loss) before income taxes												(291,561)	186,359	234,023
Provision (benefit) for income taxes:
Current												159	(10,904)	15,022
Deferred												(102,177)	79,629	69,575
Total income taxes												(102,018)	68,725	84,597
Net income (loss)	$ (190,515)	[1]	$ (29,415)	[2]	$ 4,444	$ 25,943	$ 1,752	[3],[4]	$ 36,102	$ 39,022	$ 40,758	$ (189,543)	$ 117,634	$ 149,426
Basic earnings (loss) per share	$ (3.47)		$ (0.54)		$ 0.08	$ 0.52	$ 0.04		$ 0.72	$ 0.78	$ 0.82	$ (3.60)	$ 2.36	$ 3.03
Diluted earnings (loss) per share	$ (3.47)		$ (0.54)		$ 0.08	$ 0.52	$ 0.04		$ 0.72	$ 0.78	$ 0.82	$ (3.60)	$ 2.36	$ 3.03
Average shares outstanding												52,721	48,693	48,319
Average shares outstanding assuming dilution												52,721	48,735	48,361

[1] Includes a write-down of oil and gas properties of $304,062 before income tax effect ($194,600 net of income tax effect).

[2] Includes a write-down of oil and gas properties of $47,130 before income tax effect ($30,163 net of income tax effect).

[3] Includes franchise tax settlement of $12,590 before income tax effect ($8,058 net of income tax effect).

[4] Includes loss on early extinguishment of debt of $27,279 before income tax effect ($17,459 net of income tax effect).