v2.4.0.6
Summary of Restricted Stock Activity (Detail) (Restricted Stock, USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Restricted Stock
     
Shares Outstanding      
Beginning Balance 424,248    
Granted 333,800    
Vested (206,000)    
Canceled/Forfeited (7,616)    
Ending Balance 544,432 424,248  
Expected to vest as of end of period 544,432    
Weighted Average Grant Price      
Beginning Balance $ 30.09    
Granted $ 70.12 $ 42.54 $ 28.95
Vested $ 21.55    
Canceled/Forfeited $ 61.99    
Ending Balance $ 57.15 $ 30.09  
Expected to vest as of end of period $ 57.15