Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Summary of Transactions for Non-Vested Stock Options (Detail)

v2.4.0.6
Share-Based Compensation - Summary of Transactions for Non-Vested Stock Options (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    
Weighted-Average Exercise Price Per Share, Option Outstanding at End of Year $ 37.44    
Non-vested stock options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of Shares, Options Outstanding at Beginning of Year 35,850 33,775 54,550
Number of Shares, Options Granted 221,750 25,000   
Number of Shares, Options Vested (69,037) (22,500) (19,750)
Number of Shares, Options Forfeited (5,375) (425) (1,025)
Number of Shares, Options Outstanding at End of Year 183,188 35,850 33,775
Weighted-Average Exercise Price Per Share, Option Outstanding at Beginning of Year $ 25.20 $ 17.68 $ 21.65
Weighted-Average Exercise Price Per Share, Options Granted $ 12.54 $ 9.88  
Weighted-Average Exercise Price Per Share, Options Vested $ 13.20 $ 56.54 $ 27.28
Weighted-Average Exercise Price Per Share, Options Forfeited $ 8.61 $ 64.89 $ 44.00
Weighted-Average Exercise Price Per Share, Option Outstanding at End of Year $ 12.37 $ 25.20 $ 17.68