CONSOLIDATED STATEMENTS OF OPERATIONS (in thousands, except per share data) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Operating revenues and other income:
Oil, gas, and NGL production revenue	$ 1,636,357	[1]	$ 1,253,783	[2]	$ 1,178,426	[3]
Net gain (loss) on divestiture activity	426,917		(131,028)		37,074
Other operating revenues	3,798		6,621		1,950
Total operating revenues and other income	2,067,072		1,129,376		1,217,450
Operating Expenses:
Oil, gas, and NGL production expense	487,367		507,906		597,565
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	665,313		557,036		790,745
Exploration	55,166		54,713		64,970
Impairment of proved properties	0		3,806		354,614
Abandonment and impairment of unproved properties	49,889		12,272		80,367
General and administrative	116,504		117,283		124,828
Net derivative (gain) loss	(161,832)		26,414		250,633
Other operating expenses, net	18,328		13,667		10,772
Total operating expenses	1,230,735		1,293,097		2,274,494
Income (loss) from operations	836,337		(163,721)		(1,057,044)
Interest expense	(160,906)		(179,257)		(158,685)
Gain (loss) on extinguishment of debt	(26,740)		(35)		15,722
Other non-operating income (expense), net	3,086		(800)		(1,909)
Income (loss) before income taxes	651,777		(343,813)		(1,201,916)
Income tax (expense) benefit	(143,370)		182,970		444,172
Net income (loss)	$ 508,407		$ (160,843)		$ (757,744)
Basic weighted-average common shares outstanding	111,912		111,428		76,568
Diluted weighted-average common shares outstanding	113,502		111,428		76,568
Basic net income (loss) per common share	$ 4.54		$ (1.44)		$ (9.90)
Diluted net income (loss) per common share	$ 4.48		$ (1.44)		$ (9.90)

[1] Note: Amounts may not calculate due to rounding.

[2] Note: Amounts may not calculate due to rounding.

[3] Note: Amounts may not calculate due to rounding.