Stock Compensation Plans - Summary of Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Options
Outstanding, Beginning balance (in shares) | shares	3,716,520
Granted (in shares) | shares	30,185
Exercised (in shares) | shares	(8,098)
Forfeited or expired (in shares) | shares	(4,896)
Outstanding, Ending balance (in shares) | shares	3,733,711
Options vested and expected to vest, Ending balance (in shares) | shares	3,644,575
Options exercisable, Ending balance (in shares) | shares	2,771,815
Weighted- Average Exercise Price
Outstanding, Beginning balance (usd per share) | $ / shares	$ 7.76
Granted (usd per share) | $ / shares	8.97
Exercised (usd per share) | $ / shares	3.92
Forfeited or expired (usd per share) | $ / shares	16.74
Outstanding, Ending balance (usd per share) | $ / shares	7.76
Options vested and expected to vest, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	7.73
Options exercisable, Weighted-Average Exercise Price, Ending balance (usd per share) | $ / shares	$ 7.64
Outstanding, Weighted-Average Remaining Contractual Term (Years), Ending balance	7 years 5 months 12 days
Options vested and expected to vest , Weighted-Average Remaining Contractual Term (Years), Ending balance	7 years 4 months 28 days
Options exercisable, Weighted-Average Remaining Contractual Term (Years), Ending balance	6 years 9 months 11 days
Outstanding, Aggregate Intrinsic Value, Ending balance | $	$ 8,998,083
Options vested and expected to vest , Aggregate Intrinsic Value, Ending balance | $	8,761,671
Options exercisable, Aggregate Intrinsic Value, Ending balance | $	$ 5,812,571