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Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Weighted Average Grant Date Fair Value, Granted $ 188.36 $ 81.47 $ 52.28
Restricted Stock Units [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares, Beginning Balance 292,057    
Number of shares, Granted 46,000    
Number of shares, Forfeited (12,750)    
Number of shares, Settled (91,544)    
Number of shares, Ending Balance 233,763    
Weighted Average Grant Date Fair Value, Beginning Balance $ 57.89    
Weighted Average Grant Date Fair Value, Granted $ 188.36    
Weighted Average Grant Date Fair Value, Forfeited $ 94.22    
Weighted Average Grant Date Fair Value, Settled $ 41.45    
Weighted Average Grant Date Fair Value, Ending Balance $ 87.97