Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options	1,029,657	1,158,317
Options granted	133,000	44,000
Options exercised	(120,758)	(169,535)
Options canceled, forfeited or expired - Options	(23,750)	(3,125)
Outstanding at ending period - Options	1,018,149	1,029,657
Exercisable at ending period - Options	499,599	492,557
Outstanding at beginning period - Wgtd. Avg. Exercise Price	$ 36.55	$ 34.45
Options granted - Wgtd. Avg. Exercise Price	59.37	61.78
Options exercised - Wgtd. Avg. Exercise Price	26.60	28.73
Options cancelled, forfeited, or expired - Wgtd. Avg. Exercise Price	37.16	36.73
Outstanding at ending period - Wgtd. Avg. Exercise Price	40.69	36.55
Exercisable at ending period - Wgtd. Avg. Exercise Price	$ 32.98	$ 29.84
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	8 years 10 months 2 days	8 years 7 months 2 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	5 years 6 months 11 days	5 years 1 month 24 days
Outstanding at ending period - Aggregate Intrinsic Value	$ 18,251	$ 27,638
Exercisable at ending period - Aggregate Intrinsic Value	$ 12,812	$ 16,525