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Stock Compensation Plan - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options vesting period range - start 1 year    
Options vesting period range - end 4 years    
Stock options exercisable 8,105 264,509 987,886
Restricted stock award, Expense $ 0.3 $ 1.9 $ 3.6
Options Granted on June 04, 2004 and Thereafter [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options expiration term 7 years    
Options Granted Prior to June 04, 2004 [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options expiration term 10 years    
Restricted Stock [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Restricted stock awards Service period, Minimum 1 year 6 months    
Restricted stock awards Service period, Maximum 3 years    
Restricted stock award, Expense 0.3 1.9 3.6
Deferred stock-based compensation 0 0.3  
Total fair value of restricted stock and restricted stock units that vested during the period $ 3.7 $ 4.2