Annual report pursuant to Section 13 and 15(d)

Performance-Based Restricted Share Awards Activity (Detail)

v2.4.0.6
Performance-Based Restricted Share Awards Activity (Detail) (Performance Based Restricted Stock, USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Performance Based Restricted Stock
     
Number of Shares      
Beginning Balance 533,587 722,027 161,173
Granted 270,000 20,646 564,000
Vested (132,791) (209,086)  
Forfeited/cancelled (395,539)   (3,146)
Ending Balance 275,257 533,587 722,027
Weighted-Average price      
Beginning of Period $ 23.39 $ 22.33 $ 5.04
Granted $ 22.93 $ 25.77 $ 27.18
Vested $ 12.87 $ 19.97  
Forfeited/cancelled $ 27.26   $ 5.04
Ending of Period $ 22.46 $ 23.39 $ 22.33