Summary of Stock Option Activity (Detail) - 6 months ended Jun. 30, 2015 - $ / shares	Total
Shares Subject to Outstanding Options
Beginning balance	4,249,168
Options granted	1,392,841
Options exercised	(736,163)
Options canceled	(108,928)
Ending balance	4,796,918
Weighted-Average Exercise Price Per Share
Beginning balance	$ 14.77
Options granted	35.41
Options exercised	9.51
Options canceled	25.95
Ending balance	$ 21.21