Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues and other income
Oil, natural gas, and related product sales	$ 259,030	$ 239,930	$ 776,088	$ 674,401
CO2 sales and transportation fees	6,590	6,253	18,533	19,147
Interest income and other income	939	7,802	8,576	10,429
Total revenues and other income	266,559	253,985	803,197	703,977
Expenses
Lease operating expenses	117,768	106,522	342,926	308,988
Marketing and plant operating expenses	11,816	14,452	39,758	40,645
CO2 discovery and operating expenses	1,346	861	2,452	2,539
Taxes other than income	20,233	20,401	62,848	59,997
General and administrative expenses	27,273	24,643	81,303	81,089
Interest, net of amounts capitalized of $9,416, $6,875, $22,217, and $18,944, respectively	24,546	24,778	75,785	103,007
Depletion, depreciation, and amortization	52,101	55,012	154,448	198,919
Commodity derivatives expense (income)	25,263	(21,224)	(9,712)	99,811
Gain on debt extinguishment	0	(7,826)	0	(115,095)
Write-down of oil and natural gas properties	0	75,521	0	810,921
Other expenses	0	0	0	36,232
Total expenses	280,346	293,140	749,808	1,627,053
Income (loss) before income taxes	(13,787)	(39,155)	53,389	(923,076)
Income tax provision (benefit)	(14,229)	(14,565)	17,018	(332,625)
Net income (loss)	$ 442	$ (24,590)	$ 36,371	$ (590,451)
Net income (loss) per common share
Basic	$ 0.00	$ (0.06)	$ 0.09	$ (1.60)
Diluted	$ 0.00	$ (0.06)	$ 0.09	$ (1.60)
Weighted average common shares outstanding
Basic	392,013	388,572	390,448	368,863
Diluted	393,023	388,572	392,625	368,863