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Share-based Compensation - Additional Information (Detail) (Restricted Stock, USD $)
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Restricted Stock
   
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Restricted stock awards vested and charged $ 546,000 $ 573,000
Total income tax benefit recognized related to restricted stock awards 186,000 223,000
Unrecognized compensation cost related to restricted stock awards $ 4,400,000  
Compensation cost recognition weighted average period 3 years