Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options	1,018,149	1,029,657
Options granted	30,000	133,000
Options exercised	(310,699)	(120,758)
Options canceled, forfeited or expired - Options	(30,000)	(23,750)
Outstanding at ending period - Options	707,450	1,018,149
Exercisable at ending period - Options	325,200	499,599
Outstanding at beginning period - Wgtd. Avg. Exercise Price	$ 40.69	$ 36.55
Options granted - Wgtd. Avg. Exercise Price	58.08	59.37
Options exercised - Wgtd. Avg. Exercise Price	31.28	26.60
Options cancelled, forfeited, or expired - Wgtd. Avg. Exercise Price	55.88	37.16
Outstanding at ending period - Wgtd. Avg. Exercise Price	44.92	40.69
Exercisable at ending period - Wgtd. Avg. Exercise Price	$ 37.19	$ 32.98
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	9 years 7 months 2 days	8 years 10 months 2 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	6 years 9 months 11 days	5 years 6 months 11 days
Outstanding at ending period - Aggregate Intrinsic Value	$ 34,049	$ 18,251
Exercisable at ending period - Aggregate Intrinsic Value	$ 18,167	$ 12,812