Stock-Based Compensation - Summary of Unvested Option (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Unvested, options beginning balance	309,720
Granted, options	46,500
Vested, options	(89,410)
Forfeited, options	(9,330)
Unvested, options ending balance	257,480	309,720
Unvested , weighted average grant date fair value beginning balance	$ 12.38
Granted, weighted average grant date fair value	23.74	$ 15.49	$ 9.99
Vested, weighted average grant date fair value	15.41	12.26	$ 12.95
Forfeited, weighted average grant date fair value	13.00
Unvested , weighted average grant date fair value ending balance	$ 13.36	$ 12.38