Summary of Significant Accounting Policies - Summary of Property and Equipment Including Oil and Natural Gas Properties (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Oil and natural gas properties:
Unproved properties	$ 537,958	$ 459,549
Proved properties	1,973,468	1,896,081
Gross oil and natural gas properties	2,511,426	2,355,630
Less accumulated depreciation, depletion and amortization	(1,278,869)	(1,248,200)
Total oil and natural gas properties, net	1,232,557	1,107,430
Other property and equipment	13,837	13,508
Less accumulated depreciation	(7,052)	(6,566)
Other property and equipment, net	6,785	6,942
Total property and equipment, net	$ 1,239,342	$ 1,114,372