Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Oil And Gas Revenue [Line Items]
Total revenues	$ 110,192	$ 101,863
Natural Gas Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	58,483	61,420
NGL Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	19,743	17,063
Oil Sales [Member]
Oil And Gas Revenue [Line Items]
Total revenues	31,958	20,949
Brokered Natural Gas and Marketing Revenue [Member]
Oil And Gas Revenue [Line Items]
Total revenues	$ 8	$ 2,431