Summary of Property and Equipment (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / bbl	Mar. 31, 2018 USD ($) $ / bbl	Dec. 31, 2018 USD ($)
Property, Plant and Equipment [Abstract]
Proved Oil and Gas Property, Full Cost Method	$ 1,135,580		$ 1,037,993
Unproved Oil and Gas Property, Full Cost Method	64,429		63,484
Oil and Gas Property, Full Cost Method, Gross	1,200,009		1,101,477
Other property and equipment	22,502		20,383
Total properties and equipment	1,222,511		1,121,860
Accumulated depreciation, depletion and amortization	(232,681)		(193,866)
Property and equipment, net (successful efforts method)	989,830		927,994
Unproved Oil and Gas Property excluded	64,400		63,500
Capitalized Exploratory Well Costs	300		$ 300
Undeveloped Leasehold Costs Transferred	100	$ 100
Capitalized Costs, Proved Properties	1,000	700
Interest Costs Capitalized	$ 1,200	$ 2,200
Amortization Expense Per Physical Unit of Production | $ / bbl	17.49	15.20