Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Shares Available for Grant
Beginning balance	81,948
Options authorized	2,045,785
Options granted	(1,114,013)
Options canceled	145,410
Ending balance	1,159,130
Shares Subject to Outstanding Options
Beginning balance	3,708,773
Options granted	1,114,013
Options exercised	(517,481)
Options canceled	(145,410)
Ending balance	4,159,895
Weighted-Average Exercise Price Per Share
Beginning balance	$ 9.43
Options granted	$ 25.50
Options exercised	$ 6.41
Options canceled	$ 18.26
Ending balance	$ 13.80