Employee Share-Based Compensation Plans - Summary of Stock Option Activity Under the Equity Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares Under Options, Beginning Balance	4,009,028	4,109,537
Shares under options, Granted	352,500	412,170
Shares Under Options, Exercised	(346,189)	(250,123)
Shares Under Options, Forfeited or expired	(280,106)	(262,556)
Shares Under Options, Ending Balance	3,735,233	4,009,028
Weighted Average Exercise Price, Beginning Balance	$ 3.89	$ 3.85
Shares Under Options, Vested and expected to vest at December 31, 2014	3,555,183
Weighted Average Exercise Price, Granted	$ 6.92	$ 4.18
Shares Under Options, Exercisable at December 31, 2014	2,935,009
Weighted Average Exercise Price, Exercised	$ 3.69	$ 3.39
Weighted Average Exercise Price, Forfeited or expired	$ 8.45	$ 4.30
Weighted Average Exercise Price, Ending Balance	$ 3.85	$ 3.89
Weighted Average Exercise Price, Vested and expected to vest at December 31, 2014	$ 3.79
Weighted Average Exercise Price, Exercisable at December 31, 2014	$ 3.50
Weighted Average Remaining Contractual Term, Outstanding	3 years 6 months 4 days	3 years 10 months 13 days
Weighted Average Remaining Contractual Term, Vested and Expected to vest	3 years 5 months 1 day
Weighted Average Remaining Contractual Term, Exercisable	3 years 7 days
Aggregate Intrinsic Value, Outstanding	$ 13,667	$ 12,933
Aggregate Intrinsic Value, Vested and expected to vest	10,054
Aggregate Intrinsic Value, Exercisable	$ 11,779