Summary of Stock Option Activity (Detail)	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Shares Subject to Outstanding Options
Beginning balance | shares	4,249,168
Options granted | shares	1,649,691
Options exercised | shares	(1,034,140)
Options canceled | shares	(152,365)
Ending balance | shares	4,712,354
Weighted-Average Exercise Price Per Share
Beginning balance	$ 14.77
Options granted	37.32
Options exercised	9.58
Options canceled	28.13
Ending balance	$ 23.25