Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Schedule of Restricted Stock Awards under 2007 Plan (Detail)

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Share-Based Compensation - Schedule of Restricted Stock Awards under 2007 Plan (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Shares, Restricted Stock at Beginning of Year 19,725 18,200 22,925
Number of Shares, Restricted Stock Granted   10,000  
Number of Shares, Restricted Stock Forfeited (2,000)    
Number of Shares, Restricted Stock Vested (7,225) (8,475) (4,725)
Number of Shares, Restricted Stock at End of Year 10,500 19,725 18,200
Weighted-Average Exercise Price Per Share, Restricted Stock at Beginning of Year $ 11.66 $ 14.38 $ 15.04
Weighted-Average Exercise Price Per Share, Restricted Stock Granted    $ 9.88   
Weighted-Average Exercise Price Per Share, Restricted Stock Forfeited $ 8.32      
Weighted-Average Exercise Price Per Share, Restricted Stock Vested $ 13.78 $ 15.41 $ 17.52
Weighted-Average Exercise Price Per Share, Restricted Stock at End of Year $ 10.83 $ 11.66 $ 14.38