Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Oil, natural gas liquids and natural gas sales	$ 218,723	$ 171,637	$ 395,098	$ 294,401
Gain (loss) on derivative instruments, net	38,101	(65,872)	102,647	(60,417)
Total revenues	256,824	105,765	497,745	233,984
Operating Costs and Expenses
Oil, natural gas liquids and natural gas production	43,909	42,840	85,197	90,567
Production and ad valorem taxes	13,218	11,265	26,038	22,435
Depreciation, depletion and amortization	121,549	117,035	221,201	236,397
Asset impairment	29	0	1,489	220,025
Exploration	1,998	1,520	5,634	1,762
General and administrative (including stock based compensation of $3,191 and $5,504 for the three months ended June 30, 2017 and 2016, respectively, and $6,388 and $7,975 for the six months ended June 30, 2017 and 2016, respectively)	19,792	23,548	40,191	53,073
Accretion of discount on asset retirement obligations	1,443	1,779	2,857	3,536
(Gain) loss on sale of assets and other	172	(161,097)	(1,003)	(160,875)
Total operating costs and expenses	202,110	36,890	381,604	466,920
Operating Income (Loss)	54,714	68,875	116,141	(232,936)
Other Income (Expense)
Interest expense	(9,145)	(9,038)	(18,111)	(18,871)
Other income	45	63	428	159
Total other expense	(9,100)	(8,975)	(17,683)	(18,712)
Income (Loss) Before Income Taxes	45,614	59,900	98,458	(251,648)
Income tax expense (benefit)	16,133	23,141	35,574	(85,291)
Net Income (Loss)	$ 29,481	$ 36,759	$ 62,884	$ (166,357)
Diluted Earnings Per Average Common Share (in dollars per share)	$ 0.30	$ 0.38	$ 0.64	$ (1.81)
Basic Earnings Per Average Common Share (in dollars per share)	$ 0.30	$ 0.38	$ 0.65	$ (1.81)
Diluted Average Common Shares Outstanding (in shares)	97,693	97,389	97,648	91,850
Basic Average Common Shares Outstanding (in shares)	97,189	97,067	97,165	91,850