Acquisition - Additional Information (Detail) $ in Thousands			9 Months Ended
	Aug. 25, 2018 USD ($) shares	Jan. 18, 2018 USD ($) a Well shares	Sep. 30, 2018
Flat Castle Acquisition [Member]
Business Acquisition [Line Items]
Area of land purchased | a		44,500
Purchase price		$ 90,000
Purchase price paid through shares of common stock | shares		37,800,000
Transaction costs capitalized related to acquisition		$ 1,000
Flat Castle Acquisition [Member] | Proved Oil And Gas Properties [Member]
Business Acquisition [Line Items]
Number of producing wells acquired | Well		1
Purchase price		$ 4,000
Flat Castle Acquisition [Member] | Unproved Oil and Natural Gas Properties [Member]
Business Acquisition [Line Items]
Purchase price		$ 86,000
Cardinal Midstream II, LLC [Member]
Business Acquisition [Line Items]
Acquisition completed month and year			2018-07
BRMR and Everest Merger Sub Inc. [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Purchase price paid through shares of common stock | shares	4.4259
Reverse stock split	0.066
Reverse stock split, description	15-to-1
Adjusted exchange ratio	0.29506
BRMR
Business Acquisition [Line Items]
Merger agreement termination fee	$ 12,000
Percentage of dissenting shares exceed outstanding common stock	12.00%
Costs and expenses in connection with transaction	$ 3,250
BRMR | Minimum [Member]
Business Acquisition [Line Items]
Merger agreement termination fee	12,000
BRMR | Maximum [Member]
Business Acquisition [Line Items]
Merger agreement termination fee	$ 18,000