Summarizes Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options Outstanding, beginning balance, Shares	1,674,534	1,943,176	2,129,929
Granted, Shares	524,534	605,000	510,000
Exercised, Shares	(571,723)	(731,142)	(672,753)
Forfeited, Shares	(96,500)	(142,500)	(24,000)
Stock Options Outstanding, ending balance, Shares	1,530,845	1,674,534	1,943,176
Stock Options Exercisable, Shares	439,561	632,034	1,055,176
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 19.14	$ 12.19	$ 8.82
Granted, Weighted-Average Exercise Price	41.97	30.15	19.64
Exercised, Weighted-Average Exercise Price	16.21	9.84	7.21
Forfeited, Weighted-Average Exercise Price	28.47	18.94	11.27
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	27.46	19.14	12.19
Exercisable, Weighted-Average Exercise Price	$ 12.18	$ 10.13	$ 12.21
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 11 months 19 days	5 years 1 month 6 days	5 years 3 months 22 days
Exercisable, Weighted-Average Remaining Contractual Term	3 years 6 months 4 days	3 years 11 months 19 days	4 years 6 months 29 days
Stock Options Outstanding, Aggregate Intrinsic Value	$ 30,573	$ 29,886	$ 28,379
Exercisable, Aggregate Intrinsic Value	$ 15,480	$ 16,744	$ 19,314