Stock Option Activity (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014
Options Outstanding
Outstanding at beginning of period	6,045,912
Granted	1,277,572
Exercised	(517,146)
Forfeited and cancelled	(64,620)
Outstanding at end of period	6,741,718
Weighted average exercise price
Outstanding at beginning of period	$ 7.72
Granted	$ 26.20
Exercised	$ 3.43
Forfeited and cancelled	$ 19.07
Outstanding at end of period	$ 11.44
Options Exercisable
Outstanding at beginning of period	3,195,701
Outstanding at end of period	3,433,826
Exercisable Weighted Average Exercise Price per Share
Outstanding at beginning of period	$ 3.64
Outstanding at end of period	$ 5.50