CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING REVENUES
Operating revenue	$ 2,143,716	$ 1,747,293	$ 1,194,627
Gain (loss) on derivative instruments	44,432	16,926	(38,950)
TOTAL OPERATING REVENUES	2,188,148	1,764,219	1,155,677
OPERATING EXPENSES
Direct operations	69,646	102,310	100,696
Taxes other than income	22,642	33,487	29,223
Exploration	113,820	21,526	27,662
Depreciation, depletion and amortization	417,479	568,817	590,128
Impairment of oil and gas properties	0	482,811	435,619
General and administrative	96,641	97,786	85,633
TOTAL OPERATING EXPENSES	1,401,157	1,803,428	1,716,288
Earnings (loss) on equity method investments	1,137	(100,486)	(2,477)
Loss on sale of assets	(16,327)	(11,565)	(1,857)
INCOME (LOSS) FROM OPERATIONS	771,801	(151,260)	(564,945)
Interest expense, net	73,201	82,130	88,336
Loss on debt extinguishment	0	0	4,709
Other expense (income)	463	(4,955)	1,609
Income (loss) before income taxes	698,137	(228,435)	(659,599)
Income tax expense (benefit)	141,094	(328,828)	(242,475)
NET INCOME (LOSS)	$ 557,043	$ 100,393	$ (417,124)
Earnings (loss) per share
Basic (in dollars per share)	$ 1.25	$ 0.22	$ (0.91)
Diluted (in dollars per share)	$ 1.24	$ 0.22	$ (0.91)
Weighted-average common shares outstanding
Basic (in shares)	445,538	463,735	456,847
Diluted (in shares)	447,568	465,551	456,847
Dividends per common share (in dollars per share)	$ 0.25	$ 0.17	$ 0.08
Natural gas
OPERATING REVENUES
Operating revenue	$ 1,881,150	$ 1,506,078	$ 1,022,590
Crude oil and condensate
OPERATING REVENUES
Operating revenue	48,722	212,338	151,106
Brokered natural gas
OPERATING REVENUES
Operating revenue	209,530	17,217	13,569
OPERATING EXPENSES
Operating expenses	184,198	15,252	10,785
Other
OPERATING REVENUES
Operating revenue	4,314	11,660	7,362
Transportation and gathering
OPERATING EXPENSES
Operating expenses	$ 496,731	$ 481,439	$ 436,542