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Employee Deferred Compensation Plan and Employee Stock Purchase Plan - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 1 Months Ended 12 Months Ended
Jul. 01, 2001
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Jun. 30, 2011
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]          
Percentage contribution, compensation   100.00%      
Matching percentage, employee contribution   5.00%      
Company's contributions amount   982 870 792  
Common stock under employee stock purchase plan, par value   0.10 0.10    
Employee Stock Purchase Plan
          
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]          
Number of common stock shares under employee stock purchase plan 1,000,000        
Common stock under employee stock purchase plan, par value $ 0.10        
Employee stock purchase plan offering period January 1 and July 1 of each year        
Commons stock plan available for sale under plan         995,000
Authorized common stock available for sale   941,913      
Shares of common stock purchased through the plan   40,116 54,933 60,047