Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Crude oil, natural gas and NGLs sales	$ 325,933	$ 213,602	$ 631,158	$ 403,294
Commodity price risk management gain (loss), net	(116,126)	57,932	(163,366)	138,636
Other income	2,724	3,624	5,339	6,935
Total revenues	212,531	275,158	473,131	548,865
Costs, expenses and other:
Lease operating expenses	32,260	20,028	61,896	39,817
Production taxes	22,604	15,042	42,773	27,441
Transportation, gathering and processing expenses	8,964	6,488	16,277	12,390
Exploration, geologic and geophysical expense	875	1,033	3,521	1,987
Impairment of properties and equipment	159,554	27,566	192,742	29,759
General and administrative expense	37,247	29,531	72,943	55,846
Depreciation, depletion and amortization	135,624	126,013	262,412	235,329
Accretion of asset retirement obligations	1,285	1,666	2,573	3,434
(Gain) loss on sale of properties and equipment	(351)	(532)	1,081	(692)
Provision for uncollectible note receivable	0	(40,203)	0	(40,203)
Other expenses	2,708	3,890	5,476	7,418
Total cost, expenses and other	400,770	190,522	661,694	372,526
Income (loss) from operations	(188,239)	84,636	(188,563)	176,339
Interest expense	(17,410)	(19,617)	(34,939)	(39,084)
Interest income	69	768	217	1,008
Income (loss) before income taxes	(205,580)	65,787	(223,285)	138,263
Income tax (expense) benefit	45,323	(24,537)	49,889	(50,867)
Net income (loss)	$ (160,257)	$ 41,250	$ (173,396)	$ 87,396
Earnings per share:
Basic	$ (2.43)	$ 0.63	$ (2.63)	$ 1.33
Diluted	$ (2.43)	$ 0.62	$ (2.63)	$ 1.32
Weighted-average common shares outstanding
Basic	66,066	65,859	66,012	65,804
Diluted	66,066	66,019	66,012	66,066