Quarterly report pursuant to sections 13 or 15(d)

Shareholder's Equity - Additional Information (Detail)

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Shareholder's Equity - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 9 Months Ended 64 Months Ended
Sep. 30, 2012
Sep. 30, 2012
Sep. 30, 2012
Oct. 31, 2011
Mar. 31, 2007
Capital Unit [Line Items]          
Shares authorized for repurchase         2,500,000
Shares authorized for additional repurchase       5,000,000  
Shares repurchased, shares 139,626 711,537 2,780,837    
Shares repurchased, value $ 196 $ 1,146 $ 4,391    
Options forfeited   60,922      
Unrecognized compensation cost for stock based compensation 11,802 11,802 11,802    
Unrecognized compensation cost for stock based compensation, period of recognition   2 years 8 months 12 days      
Stock Options Exercise   811,500      
Intrinsic value of options exercised   1,216      
Awards Granted during Twenty Twelve
         
Capital Unit [Line Items]          
Unrecognized compensation cost for stock based compensation $ 3,796 $ 3,796 $ 3,796    
Unrecognized compensation cost for stock based compensation, period of recognition   3 years 1 month 6 days