Stock Incentive Plans - Share-Based Compensation (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Total compensation cost for share-based payments	$ 550	$ 969	$ 2,268	$ 2,662
Weighted average grant-date fair value of equity instruments granted (per share)	$ 2.57	$ 2.25	$ 1.76	$ 2.68
Total fair value of shares vested during the period	111	100	4,823	2,534
Total intrinsic value of options exercised
Unamortized share-based payments	$ 2,132	$ 2,839	$ 2,132	$ 2,839
Weighted average period (in years) to be recognized as expense	1 year 10 months 24 days	1 year 3 months 18 days	1 year 10 months 24 days	1 year 3 months 18 days