Summary of Stock Options Issued Pursuant to Stock Incentive Plans (Detail)	9 Months Ended
	Sep. 30, 2016 USD ($) $ / shares shares
Number of Shares
Outstanding, Beginning Balance | shares	5,799,076
Granted | shares	2,284,500
Exercised | shares	(754,619)
Forfeited | shares	(351,625)
Outstanding, Ending Balance | shares	6,977,332
Number of Shares Exercisable, Ending Balance | shares	3,504,839
Weighted-Average Exercise Price
Beginning Balance | $ / shares	$ 14.37
Granted | $ / shares	17.92
Exercised | $ / shares	11.51
Forfeited | $ / shares	18.84
Ending Balance | $ / shares	15.61
Weighted-Average Exercise Price Exercisable, Ending Balance | $ / shares	$ 12.78
Weighted-Average Remaining Contractual Term (Years)
Weighted Average Remaining Contractual Term (Years), Outstanding as of end of period	6 years 9 months 7 days
Weighted-Average Remaining Contractual Term (Years), Exercisable as of end of period	4 years 10 months 17 days
Aggregate Intrinsic Value of In-the-Money Options
Aggregate Intrinsic Value of In-the-Money Options, Outstanding as of end of period | $	$ 27,141,346
Aggregate Intrinsic Value of In-the-Money Options, Exercisable as of end of period | $	$ 23,679,548