Summary of Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	4,731,483
Options granted | shares	980,215
Options exercised | shares	(10,984)
Options canceled | shares	(85,230)
Ending balance | shares	5,615,484
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 24.19
Options granted | $ / shares	32.51
Options exercised | $ / shares	15.52
Options canceled | $ / shares	28.85
Ending balance | $ / shares	$ 25.59