Condensed 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 and other income
Oil, natural gas, and related product sales	$ 250,880	$ 246,668	$ 517,058	$ 434,471
CO2 sales and transportation fees	6,555	6,622	11,943	12,894
Interest income and other income	3,749	1,858	7,637	2,627
Total revenues and other income	261,184	255,148	536,638	449,992
Expenses
Lease operating expenses	111,318	100,019	225,158	202,466
Marketing and plant operating expenses	13,877	12,999	27,942	26,193
CO2 discovery and operating expenses	513	1,071	1,106	1,678
Taxes other than income	20,175	19,504	42,615	39,596
General and administrative expenses	25,789	22,545	54,030	56,446
Interest, net of amounts capitalized of $8,147, $6,289, $12,801 and $12,069, respectively	24,061	36,058	51,239	78,229
Depletion, depreciation, and amortization	51,152	66,541	102,347	143,907
Commodity derivatives expense (income)	(10,373)	98,209	(34,975)	121,035
Gain on debt extinguishment	0	(12,278)	0	(107,269)
Write-down of oil and natural gas properties	0	479,400	0	735,400
Other expenses	0	34,688	0	36,232
Total expenses	236,512	858,756	469,462	1,333,913
Income (loss) before income taxes	24,672	(603,608)	67,176	(883,921)
Income tax provision (benefit)	10,273	(222,940)	31,247	(318,060)
Net income (loss)	$ 14,399	$ (380,668)	$ 35,929	$ (565,861)
Net income (loss) per common share
Basic	$ 0.04	$ (1.03)	$ 0.09	$ (1.58)
Diluted	$ 0.04	$ (1.03)	$ 0.09	$ (1.58)
Weighted average common shares outstanding
Basic	389,904	370,566	389,652	358,901
Diluted	391,827	370,566	392,414	358,901