Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Summary of Stock Option Transactions under Plans (Detail)

v2.4.0.6
Share-Based Compensation - Summary of Stock Option Transactions under Plans (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, Options Outstanding at End of Year 342,950    
Number of Shares, Options Exercisable at End of Year 159,762    
Weighted-Average Exercise Price Per Share, Option Outstanding at End of Year $ 37.44    
Weighted-Average Exercise Price Per Share, Options Exercisable at End of Year $ 27.68    
Stock Option Awards [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Shares, Options Outstanding at Beginning of Year 143,325 133,361 147,544
Number of Shares, Options Granted 221,750 25,000   
Number of Shares, Options Exercised (1,250)    (2,000)
Number of Shares, Options Forfeited (5,375) (425) (1,025)
Number of Shares, Options Expired (15,500) (14,611) (11,158)
Number of Shares, Options Outstanding at End of Year 342,950 143,325 133,361
Number of Shares, Options Exercisable at End of Year 159,762 107,475 99,586
Weighted-Average Exercise Price Per Share, Option Outstanding at Beginning of Year $ 81.27 $ 95.45 $ 94.26
Weighted-Average Exercise Price Per Share, Options Granted $ 12.54 $ 9.88   
Weighted-Average Exercise Price Per Share, Options Exercised $ 8.32    $ 10.80
Weighted-Average Exercise Price Per Share, Options Forfeited $ 8.61 $ 64.89 $ 136.96
Weighted-Average Exercise Price Per Share, Options Expired $ 98.76 $ 39.09 $ 91.04
Weighted-Average Exercise Price Per Share, Option Outstanding at End of Year $ 37.44 $ 81.27 $ 95.45
Weighted-Average Exercise Price Per Share, Options Exercisable at End of Year $ 66.19 $ 104.25 $ 111.52