Employee Share-Based Compensation Plans - Summary of Stock Option Activity Under the Equity Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares Under Options, Beginning Balance	3,749,783	3,735,233
Shares under options, Granted	45,000	304,000
Shares Under Options, Exercised	(883,085)	(259,549)
Shares Under Options, Forfeited or expired	(61,368)	(29,901)
Shares Under Options, Ending Balance	2,850,330	3,749,783
Weighted Average Exercise Price, Beginning Balance	$ 4.15	$ 3.85
Shares Under Options, Vested and expected to vest at December 31, 2016	2,778,665
Weighted Average Exercise Price, Granted	$ 7.61	7.05
Shares Under Options, Exercisable at December 31, 2016	2,531,819
Weighted Average Exercise Price, Exercised	$ 3.64	3.21
Weighted Average Exercise Price, Forfeited or expired	4.64	3.80
Weighted Average Exercise Price, Ending Balance	4.36	$ 4.15
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2016	4.29
Weighted Average Exercise Price, Exercisable at December 31, 2016	$ 4.02
Weighted Average Remaining Contractual Term, Outstanding	2 years 7 months 17 days	2 years 11 months 5 days
Weighted Average Remaining Contractual Term, Vested and Expected to vest	2 years 6 months 26 days
Weighted Average Remaining Contractual Term, Exercisable	2 years 4 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 8,961	$ 14,456
Aggregate Intrinsic Value, Vested and expected to vest	8,041
Aggregate Intrinsic Value, Exercisable	$ 8,810