Stock-Based Compensation - Summary of Activity Under Stock Option Plan (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at beginning period - Options | shares	1,029,657
Options granted | shares	108,000
Options exercised | shares	(86,482)
Options canceled, forfeited or expired - Options | shares	(22,500)
Outstanding at ending period - Options | shares	1,028,675
Exercisable at ending period - Options | shares	474,500
Outstanding at beginning period - Wgtd. Avg. Exercise Price	$ 36.55
Options granted - Wgtd. Avg. Exercise Price	59.84
Options exercised - Wgtd. Avg. Exercise Price	24.65
Options cancelled, forfeited, or expired - Wgtd. Avg. Exercise Price	37.14
Outstanding at ending period - Wgtd. Avg. Exercise Price	39.98
Exercisable at ending period - Wgtd. Avg. Exercise Price	$ 32.17
Outstanding at ending period - Wgtd. Avg. Remaining Contractual Term, years	8 years 9 months 26 days
Exercisable at ending period - Wgtd. Avg. Remaining Contractual Term, years	5 years 3 months 11 days
Outstanding at ending period - Aggregate Intrinsic Value | $	$ 23,782
Exercisable at ending period - Aggregate Intrinsic Value | $	$ 14,677