CONSOLIDATED STATEMENT OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING REVENUES
Natural gas	$ 1,022,590	$ 1,025,044	$ 1,590,625
Crude oil and condensate	151,106	248,211	313,889
Gain (loss) on derivative instruments	(38,950)	56,686	219,319
Brokered natural gas	13,569	16,383	34,416
Other	7,362	10,826	14,762
TOTAL OPERATING REVENUES	1,155,677	1,357,150	2,173,011
OPERATING EXPENSES
Direct operations	100,696	140,814	145,529
Transportation and gathering	436,542	427,588	349,321
Brokered natural gas	10,785	12,592	30,030
Taxes other than income	29,223	42,809	47,012
Exploration	27,662	27,460	28,746
Depreciation, depletion and amortization	590,128	622,211	632,760
Impairment of oil and gas properties and other assets	435,619	114,875	771,037
General and administrative	87,242	69,444	82,590
TOTAL OPERATING EXPENSES	1,717,897	1,457,793	2,087,025
Earnings (loss) on equity method investments	(2,477)	6,415	3,080
Gain (loss) on sale of assets	(1,857)	3,866	17,120
INCOME (LOSS) FROM OPERATIONS	(566,554)	(90,362)	106,186
Loss on debt extinguishment	4,709	0	0
Interest expense	88,336	96,911	73,785
Income (loss) before income taxes	(659,599)	(187,273)	32,401
Income tax benefit	(242,475)	(73,382)	(72,067)
NET INCOME (LOSS)	$ (417,124)	$ (113,891)	$ 104,468
Earnings (loss) per share
Basic (in dollars per share)	$ (0.91)	$ (0.28)	$ 0.25
Diluted (in dollars per share)	$ (0.91)	$ (0.28)	$ 0.25
Weighted-average common shares outstanding
Basic (in shares)	456,847	413,696	415,840
Diluted (in shares)	456,847	413,696	417,601
Dividends per common share (in dollars per share)	$ 0.0792105667127805	$ 0.08	$ 0.08