Derivative Instruments - Summary of Derivative Instrument Positions for Future Production Periods (Detail)	6 Months Ended
	Jun. 30, 2018 MMBTU $ / MMBTU bbl
Natural Gas Swaps Production Period July 2018 – March 2019 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price ($/MMBtu)	2.90
Natural Gas Swaps Production Period July 2018 – December 2018 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price ($/MMBtu)	2.80
Natural Gas Swaps Production Period July 2018 – September 2018 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price ($/MMBtu)	2.81
Natural Gas Swaps Production Period October 2018 – December 2019 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	40,000
Weighted Average Price ($/MMBtu)	2.80
Natural Gas Swaps Production Period January 2019 – December 2019 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	50,000
Weighted Average Price ($/MMBtu)	2.87
Basis Swaps Production Period April 2019 – October 2019 [Member] | Appalachia [Member] | Dominion Resources, Inc [Member] | Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	12,500
Weighted Average Price ($/MMBtu)	(0.52)
Basis Swaps Production Period April 2020 – October 2020 [Member] | Appalachia [Member] | Dominion Resources, Inc [Member] | Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	12,500
Weighted Average Price ($/MMBtu)	(0.52)
Basis Swaps Production Period January 2020 – December 2020 [Member] | Appalachia [Member] | Dominion Resources, Inc [Member] | Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price ($/MMBtu)	(0.59)
Natural Gas Three-way Collars Production Period July 2018 – March 2019 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price, Floor ($/MMBtu)	3.00
Natural Gas Three-way Collars Production Period July 2018 – March 2019 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price, Floor ($/MMBtu)	2.50
Natural Gas Three-way Collars Production Period July 2018 – March 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price, Ceiling ($/MMBtu)	3.40
Natural Gas Three-way Collars Production Period July 2018 – December 2018 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	40,000
Weighted Average Price, Floor ($/MMBtu)	3.11
Natural Gas Three-way Collars Production Period July 2018 – December 2018 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	60,000
Weighted Average Price, Floor ($/MMBtu)	2.80
Natural Gas Three-way Collars Production Period July 2018 – December 2018 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	100,000
Weighted Average Price, Floor ($/MMBtu)	2.50
Natural Gas Three-way Collars Production Period July 2018 – December 2018 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	100,000
Weighted Average Price, Ceiling ($/MMBtu)	3.36
Natural Gas Three-way Collars Production Period October 2018 – December 2019 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price, Floor ($/MMBtu)	2.75
Natural Gas Three-way Collars Production Period October 2018 – December 2019 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price, Floor ($/MMBtu)	2.30
Natural Gas Three-way Collars Production Period October 2018 – December 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	20,000
Weighted Average Price, Ceiling ($/MMBtu)	3.10
Natural Gas Three-way Collars Production Period January 2019 – December 2019 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	57,500
Weighted Average Price, Floor ($/MMBtu)	2.72
Natural Gas Three-way Collars Production Period January 2019 – December 2019 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	57,500
Weighted Average Price, Floor ($/MMBtu)	2.30
Natural Gas Three-way Collars Production Period January 2019 – December 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	57,500
Weighted Average Price, Ceiling ($/MMBtu)	3.02
Natural Gas Call/Put Options Production Period July 2018 – December 2018 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	40,000
Weighted Average Price ($/MMBtu)	3.75
Natural Gas Call/Put Options Production Period January 2019 – March 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price ($/MMBtu)	3.50
Natural Gas Call/Put Options Production Period April 2019 – December 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	30,000
Weighted Average Price ($/MMBtu)	3.00
Natural Gas Call/Put Options Production Period January 2019 – December 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (MMBtu/d) | MMBTU	10,000
Weighted Average Price ($/MMBtu)	4.75
Oil Swaps Production Period July 2018 – March 2019 [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price ($/MMBtu)	61.00
Volume (Bbls/d) | bbl	1,000
Oil Three-way Collars Production Period July 2018 – December 2018 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor ($/MMBtu)	45.00
Volume (Bbls/d) | bbl	4,000
Oil Three-way Collars Production Period July 2018 – December 2018 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor ($/MMBtu)	35.00
Volume (Bbls/d) | bbl	4,000
Oil Three-way Collars Production Period July 2018 – December 2018 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling ($/MMBtu)	53.47
Volume (Bbls/d) | bbl	4,000
Oil Three-way Collars Production Period January 2019 – December 2019 [Member] | Put Option [Member] | Purchase [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor ($/MMBtu)	50.00
Volume (Bbls/d) | bbl	2,000
Oil Three-way Collars Production Period January 2019 – December 2019 [Member] | Put Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Floor ($/MMBtu)	40.00
Volume (Bbls/d) | bbl	2,000
Oil Three-way Collars Production Period January 2019 – December 2019 [Member] | Call Option [Member] | Sold [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Weighted Average Price, Ceiling ($/MMBtu)	60.56
Volume (Bbls/d) | bbl	2,000