Summary of Stock Option Activity (Detail) - Employee Stock Option	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Shares Subject to Outstanding Stock Options
Beginning balance | shares	4,731,483
Options granted | shares	1,465,086
Options exercised | shares	(16,330)
Options canceled | shares	(210,869)
Ending balance | shares	5,969,370
Weighted-Average Exercise Price Per Share
Beginning balance | $ / shares	$ 24.19
Options granted | $ / shares	29.82
Options exercised | $ / shares	14.23
Options canceled | $ / shares	28.59
Ending balance | $ / shares	$ 25.44