CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues and other income:
Oil, gas, and NGL production revenue	$ 1,178,426	$ 1,499,905	$ 2,481,544
Net gain on divestiture activity	37,074	43,031	646
Marketed gas system revenue	0	9,485	24,897
Other operating revenues	1,950	4,544	15,220
Total operating revenues and other income	1,217,450	1,556,965	2,522,307
Operating Expenses:
Oil, gas, and NGL production expense	597,565	723,633	715,878
Depletion, depreciation, amortization, and asset retirement obligation liability accretion	790,745	921,009	767,532
Exploration	65,641	120,569	129,857
Impairment of proved properties	354,614	468,679	84,480
Abandonment and impairment of unproved properties	80,367	78,643	75,638
Impairment of other property and equipment	0	49,369	0
General and administrative	126,428	157,668	167,103
Change In Net Profits Plan Liability	(7,200)	(19,525)	(29,849)
Net derivative (gain) loss	250,633	(408,831)	(583,264)
Marketed gas system expense	0	13,922	24,460
Other operating expenses	17,972	30,612	4,658
Total operating expenses	2,276,765	2,135,748	1,356,493
Income (loss) from operations	(1,059,315)	(578,783)	1,165,814
Non-operating income (expense):
Interest expense	(158,685)	(128,149)	(98,554)
Gain (loss) on extinguishment of debt	15,722	(16,578)	0
Other, net	362	649	(2,561)
Income (loss) before income taxes	(1,201,916)	(722,861)	1,064,699
Income tax (expense) benefit	444,172	275,151	(398,648)
Net income (loss)	$ (757,744)	$ (447,710)	$ 666,051
Earnings Per Share, Basic [Abstract]
Basic weighted-average common shares outstanding	76,568	67,723	67,230
Basic net income (loss) per common share	$ (9.90)	$ (6.61)	$ 9.91
Earnings Per Share, Diluted [Abstract]
Diluted weighted-average common shares outstanding	76,568	67,723	68,044
Diluted net income (loss) per common share	$ (9.90)	$ (6.61)	$ 9.79