FRESH START ACCOUNTING - Additional Information (Details) - USD ($)				1 Months Ended		2 Months Ended	3 Months Ended		4 Months Ended	6 Months Ended
	Mar. 01, 2017	Feb. 28, 2017	Feb. 27, 2017	Mar. 31, 2017	Oct. 31, 2016	Feb. 28, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Fresh-Start Adjustment [Line Items]
Accumulated deficit		$ 554,628,000				$ 554,628,000	$ 288,947,000		$ 288,947,000
Enterprise value		$ 419,720,000				419,720,000
Annual escalation adjustment rate		2.00%
Expected period for development to begin		5 years
Proved reserves		$ 380,800,000				380,800,000
Probable and possible reserves		16,800,000				16,800,000
Unevaluated properties reserves		80,200,000				80,200,000
Fair value of asset retirement obligations		$ 290,067,000				290,067,000
Credit-adjusted risk free rate		12.00%
Repayment of outstanding borrowings under Pre-Emergence Credit Agreement		$ 341,500,000							$ 0
New shares issued in reorganization (in shares)	20,000,000.0	20,000,000		1,195
Emergence and success fees		$ 15,180,000
Professional fees		2,600,000
Predecessor Company's Common Stockholders
Fresh-Start Adjustment [Line Items]
Warrants issued in reorganization (in shares)	3,500,000.0
Exercise price of warrants or rights (in usd per share)							$ 42.04		$ 42.04
Exercise period for warrants							4 years
Senior Notes | 7 ½% Senior Notes due 2022
Fresh-Start Adjustment [Line Items]
Aggregate principal amount of senior subordinated notes	$ 225,000,000.0
Predecessor
Fresh-Start Adjustment [Line Items]
Accumulated deficit		(3,610,000)				(3,610,000)					$ (637,282,000)	$ (39,789,000)
Loss on contract termination										$ 20,000,000
Repayment of outstanding borrowings under Pre-Emergence Credit Agreement						$ 341,500,000				$ 135,500,000
New shares issued in reorganization (in shares)						47,390		12,100		62,200
Emergence and success fees						$ (10,600,000)
Professional fees						9,100,000
Appalachia Properties | Disposal Group, Disposed of by Sale
Fresh-Start Adjustment [Line Items]
Indemnity escrow release			$ 10,000,000
Revaluation of Assets
Fresh-Start Adjustment [Line Items]
Write off of unamortized debt issuance costs		2,577,000
Revaluation of Assets | Tug Hill, Inc
Fresh-Start Adjustment [Line Items]
Net reimbursement in connection with the sale of asset		699,000				699,000
Loss on contract termination					$ 1,750,000
Revaluation of Liabilities | Senior Notes | 7 ½% Senior Notes due 2022
Fresh-Start Adjustment [Line Items]
Aggregate principal amount of senior subordinated notes		225,000,000				225,000,000
Revaluation of Liabilities | Predecessor
Fresh-Start Adjustment [Line Items]
Repayment of outstanding borrowings under Pre-Emergence Credit Agreement						341,500,000
Revaluation of Liabilities | Leasing Arrangement
Fresh-Start Adjustment [Line Items]
Loss on contract termination		395,000
Revaluation of Liabilities | Appalachia Properties | Disposal Group, Disposed of by Sale
Fresh-Start Adjustment [Line Items]
Settlement of a property tax accrual		2,598,000				$ 2,598,000
Revaluation of Liabilities | Deferred Bonus | 2016 Incentive Plan
Fresh-Start Adjustment [Line Items]
Deferred compensation arrangement compensation expense		$ 2,008,000
Exchange of Stock for Stock
Fresh-Start Adjustment [Line Items]
Estimated fair value of the warrants (in usd per share)		$ 4.43				$ 4.43
Exchange of Stock for Stock | Predecessor Company's Common Stockholders
Fresh-Start Adjustment [Line Items]
Warrants issued in reorganization (in shares)		3,500,000
Exercise price of warrants or rights (in usd per share)		$ 42.04				$ 42.04
Exercise period for warrants		4 years
Exchange of Stock for Stock | Senior Notes | 7 ½% Senior Notes due 2022 | Predecessor Company's Noteholders
Fresh-Start Adjustment [Line Items]
New shares issued in reorganization (in shares)		1,000,000.0
Exchange of Stock for Stock | Convertible Debt | 1 ¾% Senior Convertible Notes due 2017 | Predecessor Company's Noteholders
Fresh-Start Adjustment [Line Items]
New shares issued in reorganization (in shares)		19,000,000.0
Income Approach Valuation Technique
Fresh-Start Adjustment [Line Items]
Discounted weighted average cost of capital rate		12.50%
Minimum
Fresh-Start Adjustment [Line Items]
Enterprise value		$ 300,000,000				$ 300,000,000
Maximum
Fresh-Start Adjustment [Line Items]
Enterprise value		450,000,000				450,000,000
Accumulated Deficit
Fresh-Start Adjustment [Line Items]
Accumulated deficit		0				0	$ (266,074,000)		$ (266,074,000)
Accumulated Deficit | Predecessor
Fresh-Start Adjustment [Line Items]
Accumulated deficit		$ (1,665,892,000)				$ (1,665,892,000)					$ (2,296,209,000)	$ (1,705,623,000)