Stock-Based Compensation - Summary of Company's Stock Option Plan Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted, Number of options	110,000	110,000
Exercised, Number of Options	0	(30,000)	(60,000)
Outstanding, Number of Options	240,000	130,000	50,000	110,000
Exercisable, Number of Options	47,500
Granted, Weighted Average Exercise Price	$ 40.00	$ 40.00
Exercised, Weighted Average Exercise Price		2.50	$ 2.50
Outstanding, Weighted Average Exercise Price	37.19	$ 34.82	$ 4.02	$ 3.19
Exercisable, Weighted-Average Exercise Price	$ 25.81
Outstanding, Weighted-Average Remaining Contractual Term	8 years 9 months 18 days	8 years 2 months 12 days	2 years 3 months 18 days	2 years 3 months 18 days
Exercisable, Weighted-Average Remaining Contractual Term	5 years 9 months 18 days
Outstanding, Aggregate Intrinsic Value	$ 3,278	$ 472	$ 1,773	$ 3,482
Exercisable, Aggregate Intrinsic Value	$ 1,189