Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options | shares	1,216,700
Options granted | shares	40,000
Options exercised | shares	(5,500)
Options canceled, forfeited, or expired | shares	(22,500)
Outstanding at ending period - Options | shares	1,228,700
Exercisable at ending period - Options | shares	613,700
Outstanding at beginning period - Wgtd. Avg. Exercise Price | $ / shares	$ 28.48
Options granted - Wgtd. Avg. Exercise Price | $ / shares	55.38
Options exercised - Wgtd. Avg. Exercise Price | $ / shares	28.35
Options cancelled, forfeited, or expired - Wgtd. Avg. Exercise Price | $ / shares	51.83
Outstanding at ending period - Wgtd. Avg. Exercise Price | $ / shares	28.93
Exercisable at ending period - Wgtd. Avg. Exercise Price | $ / shares	$ 21.78
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	9 years 4 months 20 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	6 years 11 months 23 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 28,536
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 18,639