Quarterly report pursuant to Section 13 or 15(d)

Restricted Common Stock and Stock Appreciation Rights ("SARs") - Additional Information (Detail)

v2.4.0.8
Restricted Common Stock and Stock Appreciation Rights ("SARs") - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of stock options, redemption or cancelation 0 0 0 0
Share based compensation expenses $ 2,053 $ 1,760 $ 4,679 $ 3,943
Notes receivable from employees [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Notes issued, interest rate     5.00%  
Notes issued, interest rate     6.00%  
Notes issued, payment date     Apr. 15, 2016  
Employee Stock Option [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Options issued expiration period     One year or less  
Deferred stock units [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted common stock issued, vesting period     5 years  
Deferred stock units [Member] | Minimum [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted common stock issued, vesting period     3 years  
Deferred stock units [Member] | Maximum [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted common stock issued, vesting period     5 years  
Restricted common stock [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized stock-based compensation expenses recognition period     4 years  
Restricted common stock and SARs [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized stock-based compensation expenses recognition period     4 years