Summary of Stock Option Activity (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	4,249,168
Options granted | shares	1,815,991
Options exercised | shares	(1,095,486)
Options canceled | shares	(238,190)
Ending balance | shares	4,731,483
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 14.77
Options granted | $ / shares	38.33
Options exercised | $ / shares	10.14
Options canceled | $ / shares	26.26
Ending balance | $ / shares	$ 24.19