Stock Option Plans and Restricted Stock Awards - Option Activity under Company's Stock Option Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding, Number of Stock Options, Beginning Balance	2,106,000
Granted, Number of Stock Options Outstanding	169,000	45,000	248,000
Exercised, Number of Stock Options Outstanding	(512,000)
Forfeited or expired, Number of Stock Options Outstanding	(75,000)
Outstanding, Number of Stock Options, Ending Balance	1,688,000	2,106,000
Vested or expected to vest, Number of Stock Options Outstanding	1,646,000
Exercisable, Number of Stock Options Outstanding	1,317,000
Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 10.61
Granted, Weighted Average Exercise Price	$ 14.80
Exercised, Weighted Average Exercise Price	$ 10.79
Forfeited or expired, Weighted Average Exercise Price	$ 11.83
Outstanding, Weighted Average Exercise Price, Ending Balance	$ 10.92	$ 10.61
Vested or expected to vest, Weighted Average Exercise Price	$ 10.90
Exercisable, Weighted Average Exercise Price	$ 10.41
Outstanding, Weighted Average Remaining Contractual Term	4 years 6 months 18 days
Vested or expected to vest, Weighted Average Remaining Contractual Term	4 years 5 months 23 days
Exercisable, Weighted Average Remaining Contractual Term	3 years 7 months 6 days
Outstanding, Aggregate Intrinsic Value	$ 8,618
Vested or expected to vest, Aggregate Intrinsic Value	8,431
Exercisable, Aggregate Intrinsic Value	$ 7,390