Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options | shares	707,450
Options granted | shares	25,000
Options exercised | shares	(93,325)
Outstanding at ending period - Options | shares	639,125
Exercisable at ending period - Options | shares	277,250
Outstanding at beginning period - Wgtd. Avg. Exercise Price | $ / shares	$ 44.92
Options granted - Wgtd. Avg. Exercise Price | $ / shares	91.39
Options exercised - Wgtd. Avg. Exercise Price | $ / shares	34.90
Outstanding at ending period - Wgtd. Avg. Exercise Price | $ / shares	48.20
Exercisable at ending period - Wgtd. Avg. Exercise Price | $ / shares	$ 38.77
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	9 years 8 months 26 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	6 years 10 months 6 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 30,933
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 16,034