Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 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	(27,300)
Options canceled, forfeited, or expired | shares	(22,500)
Outstanding at ending period - Options | shares	1,206,900
Exercisable at ending period - Options | shares	648,400
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	22.37
Options cancelled, forfeited, or expired - Wgtd. Avg. Exercise Price | $ / shares	51.83
Outstanding at ending period - Wgtd. Avg. Exercise Price | $ / shares	29.07
Exercisable at ending period - Wgtd. Avg. Exercise Price | $ / shares	$ 22.49
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	9 years 2 months 12 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	7 years 29 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 32,090
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 21,506