Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options | shares	1,273,625
Options granted | shares	30,000
Options exercised | shares	(76,950)
Outstanding at ending period - Options | shares	1,226,675
Exercisable at ending period - Options | shares	520,925
Outstanding at beginning period - Wgtd. Avg. Exercise Price | $ / shares	$ 25.90
Options granted - Wgtd. Avg. Exercise Price | $ / shares	54.73
Options exercised - Wgtd. Avg. Exercise Price | $ / shares	16.02
Outstanding at ending period - Wgtd. Avg. Exercise Price | $ / shares	27.22
Exercisable at ending period - Wgtd. Avg. Exercise Price | $ / shares	$ 20.77
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	10 years
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	7 years 3 months 18 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 31,747
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 16,840