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Stockholders' Equity - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Stockholders Equity [Line Items]      
Retained earnings from which dividends may not be paid without prior approval, total 14,312,000 14,130,000 15,251,000
Common Stock, Capital Shares Reserved for Future Issuance 313,919    
Employee Stock Purchase
      
Stockholders Equity [Line Items]      
Employees to buy stock under options granted 85.00%    
Options are vested when granted and will expire no later than 27 months    
Shares of common stock reserved for issuance under the plan total 48,011    
Opportunity to receive additional shares of common stock in lieu of cash dividend 95.00%    
Shares of common stock purchased 19,069 15,818 19,076
Common Stock, Capital Shares Reserved for Future Issuance 221,510