Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Options Outstanding
Outstanding, beginning of period	1,232,862
Granted	81,552
Exercised	(144,210)
Canceled	(3,070)
Outstanding, end of period	1,167,134	1,232,862
Exercisable at September 30, 2014	815,518
Weighted-Average Exercise Price per Share
Outstanding, beginning of period	$ 24.36
Granted	$ 73.20
Exercised	$ 21.11
Canceled	$ 52.73
Outstanding, end of period	$ 28.10	$ 24.36
Exercisable at September 30, 2014	$ 20.69
Weighted-Average Remaining Contractual Life
Weighted- Average Remaining Contractual Life, outstanding	5 years 8 months 12 days	6 years 1 month 6 days
Exercisable at September 30, 2014	4 years 9 months 18 days
Aggregate Intrinsic Value
Outstanding, beginning of period	$ 61,530
Granted	661
Exercised	(8,682)
Canceled	(88)
Outstanding, end of period	62,101	61,530
Exercisable at September 30, 2014	$ 49,435