Stock-Based Compensation Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Y	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance	3,469
Stock grants counted against the total shares for every share issued	2.7
Stock-based compensation arrangement maximum assumption expected period, years	10
Description and terms of 2003 incentive stock plan	Incentive stock awards are granted under the Company’s 2003 Incentive Stock Plan, as amended and restated in October 2008 (the “2003 Stock Plan”). Under the 2003 Stock Plan, an aggregate of 3,469 shares of common stock were reserved for issuance. Of this amount, stock grants count against the total shares available under the 2003 Stock Plan as 2.7 shares for every one share issued, while options (and stock appreciation rights (“SAR”) settled in shares) count against the total shares available as one share for every one share issued on the exercise of an option (or SAR). The exercise price of each option granted under the 2003 Stock Plan may not be less than the market price of the Company’s common stock on the date of the option grant and all options may have a maximum life of ten years. Participants receiving restricted stock grants are generally eligible to vote such shares and receive dividends on such shares. Substantially all stock option and restricted stock grants are subject to annual vesting provisions (generally three to five years) as determined by the compensation committee overseeing the 2003 Stock Plan.
Maximum number of shares issuable under the ESPP	300
Percentage of share purchase price	85.00%
Discount on the share purchases	15.00%
Employee stock purchase plan description, compensation expense	$ 223	$ 198	$ 384
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense relating to the restricted stock	2,334	2,004	2,309
Unrecognized compensation cost related to unvested stock options	2,583
Unrecognized compensation costs, weighted average period of recognition, years	2 years
Total Intrinsic value of restricted shares vested	3,892	4,246	3,561
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense relating to the restricted stock	380	379	317
Unrecognized compensation costs, weighted average period of recognition, years	1 year 8 months 12 days
Unrecognized compensation cost related to unvested stock options	419
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of stock options exercised	$ 15,808	$ 5,525	$ 2,827
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award vesting period, maximum (in years)	3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award vesting period, maximum (in years)	5 years