Summarizes Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options Outstanding, beginning balance, Shares	1,530,845	1,674,534	1,943,176
Granted, Shares	862,000	524,534	605,000
Exercised, Shares	(112,875)	(571,723)	(731,142)
Forfeited, Shares	(176,500)	(96,500)	(142,500)
Stock Options Outstanding, ending balance, Shares	2,103,470	1,530,845	1,674,534
Stock Options Exercisable, Shares	675,152	439,561	632,034
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 27.46	$ 19.14	$ 12.19
Granted, Weighted-Average Exercise Price	40.87	41.97	30.15
Exercised, Weighted-Average Exercise Price	13.24	16.21	9.84
Forfeited, Weighted-Average Exercise Price	39.32	28.47	18.94
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	32.72	27.46	19.14
Exercisable, Weighted-Average Exercise Price	$ 21.40	$ 12.18	$ 10.13
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 10 months 10 days	4 years 11 months 19 days	5 years 1 month 6 days
Exercisable, Weighted-Average Remaining Contractual Term	3 years 5 months 12 days	3 years 6 months 4 days	3 years 11 months 19 days
Stock Options Outstanding, Aggregate Intrinsic Value	$ 12,265	$ 30,573	$ 29,886
Exercisable, Aggregate Intrinsic Value	$ 9,646	$ 15,480	$ 16,744