Commitments and Contingencies - Schedule of Other Commitments Assumed in Relation to Certain Firm Transportation and Gas Processing Gathering and Compression Service Agreements (Detail) - BRMR and Everest Merger Sub Inc. [Member] $ in Thousands	Sep. 30, 2019 USD ($)
Other Commitments [Line Items]
2019	$ 27,435
2020	36,549
2021	36,503
2022	36,503
2023	34,608
Thereafter	231,940
Total	403,538
Firm Transportation [Member]
Other Commitments [Line Items]
2019	14,562	[1]
2020	19,416	[1]
2021	19,416	[1]
2022	19,416	[1]
2023	18,047	[1]
Thereafter	92,395	[1]
Total	183,252	[1]
Gas Processing, Gathering, and Compression Services [Member]
Other Commitments [Line Items]
2019	12,873	[2]
2020	17,133	[2]
2021	17,087	[2]
2022	17,087	[2]
2023	16,561	[2]
Thereafter	139,545	[2]
Total	$ 220,286	[2]

[1] Firm transportation - Firm transportation agreements with various pipelines to facilitate the delivery of production to market. These contracts commit the Company to transport minimum daily natural gas volumes at a negotiated rate or pay for any deficiencies at a specified reservation fee rate. The amounts in this table represent the minimum daily volumes at the reservation fee rate. The values in the table represent the gross amounts that the Company is committed to pay and does not deduct amounts that other parties are responsible for as a result of cost sharing arrangements with working interest partners. The Company will record in its Consolidated Financial Statements its proportionate share of costs based on its working interest.

[2] Gas processing, gathering, and compression services - Contractual commitments for gas processing, gathering and compression service agreements represent minimum commitments under long-term gas processing and gathering agreements as well as various gas compression agreements. The values in the table represent the gross amounts that the Company is committed to pay and does not deduct amounts that other parties are responsible for as a result of cost sharing arrangements with working interest partners. The Company will record in its Consolidated Financial Statements its proportionate share of costs based on its working interest