Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUES
Natural gas, oil and natural gas liquids sales	$ 380,178	$ 223,015	$ 234,601
Brokered natural gas and marketing revenue	3,481	12,019	20,720
Total revenues	383,659	235,034	255,321
OPERATING EXPENSES
Lease operating	20,525	9,023	13,904
Transportation, gathering and compression	124,839	109,226	85,846
Production and ad valorem taxes	8,490	7,927	3,722
Brokered natural gas and marketing expense	3,191	12,268	26,173
Depreciation, depletion and amortization	118,818	92,948	244,750
Exploration	50,208	52,775	116,211
General and administrative	44,553	39,431	46,409
Rig termination and standby	1	3,846	9,672
Impairment of proved oil and gas properties		17,665	691,334
Accretion of asset retirement obligations	544	391	1,623
(Gain) loss on sale of assets	(179)	6,936	(4,737)
Total operating expenses	370,990	352,436	1,234,907
OPERATING INCOME (LOSS)	12,669	(117,402)	(979,586)
OTHER INCOME (EXPENSE)
Gain (loss) on derivative instruments	45,365	(52,338)	56,021
Interest expense, net	(49,490)	(50,789)	(53,400)
Gain (loss) on early extinguishment of debt		14,489	(59,392)
Other income (expense)	(19)	(149)	400
Total other income (expense), net	(4,144)	(88,787)	(56,371)
INCOME (LOSS) BEFORE INCOME TAXES	8,525	(206,189)	(1,035,957)
INCOME TAX BENEFIT (EXPENSE)		(546)	74,166
NET INCOME (LOSS)	$ 8,525	$ (206,735)	$ (961,791)
NET INCOME (LOSS) PER COMMON SHARE
Basic	$ 0.03	$ (0.86)	$ (4.41)
Diluted	$ 0.03	$ (0.86)	$ (4.41)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING
Basic	262,181	241,434	217,897
Diluted	265,182	241,434	217,897