DERIVATIVE INSTRUMENTS - Outstanding Derivative Contracts (Details) - Outstanding at end of period	6 Months Ended
	Jun. 30, 2018 MMBTU $ / bbl $ / MMBTU bbl
Derivative Contract Oil Collar WTI Index | 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	5,888,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	50.36
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	61.06
Derivative Contract Oil Collar WTI Index | Third Quarter - 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	3,220,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	49.80
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	60.49
Derivative Contract Oil Collar WTI Index | Fourth Quarter - 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	2,668,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	51.03
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	61.74
Derivative Contract Oil Collar WTI Index | 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	6,371,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	52.81
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	65.04
Derivative Contract Oil Collar WTI Index | First Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	2,070,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	51.83
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	63.77
Derivative Contract Oil Collar WTI Index | Second Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	2,093,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	51.83
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	63.77
Derivative Contract Oil Collar WTI Index | Third Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	1,472,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	53.50
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	67.13
Derivative Contract Oil Collar WTI Index | Fourth Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	736,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl) | $ / bbl	57.00
Weighted Avg Price - Ceiling (USD per Bbl) | $ / bbl	68.04
Derivative Contract Gas Collar PEPL Index | 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	21,160,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.16
Weighted Avg Price - Ceiling (USD per Bbl)	2.45
Derivative Contract Gas Collar PEPL Index | Third Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	11,960,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.19
Weighted Avg Price - Ceiling (USD per Bbl)	2.48
Derivative Contract Gas Collar PEPL Index | Fourth Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	9,200,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.12
Weighted Avg Price - Ceiling (USD per Bbl)	2.42
Derivative Contract Gas Collar PEPL Index | 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	24,570,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.02
Weighted Avg Price - Ceiling (USD per Bbl)	2.36
Derivative Contract Gas Collar PEPL Index | First Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	8,100,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.08
Weighted Avg Price - Ceiling (USD per Bbl)	2.39
Derivative Contract Gas Collar PEPL Index | Second Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	8,190,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	2.08
Weighted Avg Price - Ceiling (USD per Bbl)	2.39
Derivative Contract Gas Collar PEPL Index | Third Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	5,520,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.92
Weighted Avg Price - Ceiling (USD per Bbl)	2.26
Derivative Contract Gas Collar PEPL Index | Fourth Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	2,760,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.90
Weighted Avg Price - Ceiling (USD per Bbl)	2.33
Derivative Contract Gas Collar Perm EP | 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	16,560,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.87
Weighted Avg Price - Ceiling (USD per Bbl)	2.09
Derivative Contract Gas Collar Perm EP | Third Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	9,200,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.92
Weighted Avg Price - Ceiling (USD per Bbl)	2.14
Derivative Contract Gas Collar Perm EP | Fourth Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	7,360,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.81
Weighted Avg Price - Ceiling (USD per Bbl)	2.03
Derivative Contract Gas Collar Perm EP | 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	19,110,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.64
Weighted Avg Price - Ceiling (USD per Bbl)	1.86
Derivative Contract Gas Collar Perm EP | First Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	6,300,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.73
Weighted Avg Price - Ceiling (USD per Bbl)	1.95
Derivative Contract Gas Collar Perm EP | Second Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	6,370,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.73
Weighted Avg Price - Ceiling (USD per Bbl)	1.95
Derivative Contract Gas Collar Perm EP | Third Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	4,600,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.50
Weighted Avg Price - Ceiling (USD per Bbl)	1.74
Derivative Contract Gas Collar Perm EP | Fourth Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	1,840,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.55
Derivative Contract Gas Collar Waha | 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	1,840,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | Third Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	920,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | Fourth Quarter - 2018
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	920,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	3,650,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | First Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	900,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | Second Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	910,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | Third Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	920,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Gas Collar Waha | Fourth Quarter - 2019
Fair values of derivative assets and liabilities
Volume (MMBtu) | MMBTU	920,000
Weighted Average Price
Weighted Avg Price - Floor (USD per Bbl)	1.35
Weighted Avg Price - Ceiling (USD per Bbl)	1.56
Derivative Contract Oil Basis Swaps WTI Midland Index | 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	4,508,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(4.19)
Derivative Contract Oil Basis Swaps WTI Midland Index | Third Quarter - 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	2,484,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(3.89)
Derivative Contract Oil Basis Swaps WTI Midland Index | Fourth Quarter - 2018
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	2,024,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(4.56)
Derivative Contract Oil Basis Swaps WTI Midland Index | 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	5,279,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(6.16)
Derivative Contract Oil Basis Swaps WTI Midland Index | First Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	1,710,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(5.17)
Derivative Contract Oil Basis Swaps WTI Midland Index | Second Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	1,729,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(5.17)
Derivative Contract Oil Basis Swaps WTI Midland Index | Third Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	1,288,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(6.84)
Derivative Contract Oil Basis Swaps WTI Midland Index | Fourth Quarter - 2019
Fair values of derivative assets and liabilities
Volume (Bbls) | bbl	552,000
Weighted Average Price
Weighted Avg Differential (USD per Bbl) | $ / bbl	(10.73)