Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues and other income	$ 1,473,625	$ 1,129,786	$ 975,596
Expenses
Taxes other than income	104,670	87,207	77,892
General and administrative expenses	71,495	101,806	109,926
Interest, net of amounts capitalized of $37,079, $30,762 and $25,982, respectively	69,688	99,263	125,145
Depletion, depreciation, and amortization	216,449	207,713	846,043
Commodity derivatives expense (income)	(21,087)	77,576	127,944
Gain on Debt Extinguishment	0	0	115,095
Write-down of oil and natural gas properties	0	0	810,921
Other expenses	79,941	7,003	37,402
Total expenses	1,063,694	1,083,286	2,495,943
Income (loss) before income taxes	409,931	46,500	(1,520,347)
Income tax provision (benefit)	87,233	(116,652)	(544,170)
Net income (loss)	$ 322,698	$ 163,152	$ (976,177)
Net income (loss) per common share
Basic	$ 0.75	$ 0.42	$ (2.61)
Diluted	$ 0.71	$ 0.41	$ (2.61)
Weighted average common shares outstanding
Basic	432,483	390,928	373,859
Diluted	456,169	395,921	373,859
Other income
Revenues and other income	$ 19,891	$ 13,938	$ 15,029
Marketing and plant operating expenses
Operating costs and expenses	50,002	51,820	57,454
Oil, natural gas, and related products
Revenues and other income	1,422,589	1,089,666	935,751
Operating costs and expenses	489,720	447,799	414,937
CO2
Revenues and other income	31,145	26,182	24,816
Operating costs and expenses	$ 2,816	$ 3,099	$ 3,374