Summary of Stock Options Issued Pursuant to Stock Incentive Plans (Detail)	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Number of Shares
Outstanding, Beginning Balance | shares	5,799,076
Granted | shares	2,284,500
Exercised | shares	(691,655)
Forfeited | shares	(150,567)
Outstanding, Ending Balance | shares	7,241,354
Number of Shares Exercisable, Ending Balance | shares	3,583,017
Weighted-Average Exercise Price
Beginning Balance | $ / shares	$ 14.37
Granted | $ / shares	17.92
Exercised | $ / shares	11.46
Forfeited | $ / shares	19.04
Ending Balance | $ / shares	15.67
Weighted-Average Exercise Price Exercisable, Ending Balance | $ / shares	$ 12.81
Weighted-Average Remaining Contractual Term (Years)
Weighted Average Remaining Contractual Term (Years), Outstanding as of end of period	7 years 2 months 16 days
Weighted-Average Remaining Contractual Term (Years), Exercisable as of end of period	5 years 2 months 27 days
Aggregate Intrinsic Value of In-the-Money Options
Aggregate Intrinsic Value of In-the-Money Options, Outstanding as of end of period | $	$ 28,633,811
Aggregate Intrinsic Value of In-the-Money Options, Exercisable as of end of period | $	$ 24,540,121