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Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) (Restricted Stock Units [Member], USD $)
3 Months Ended
Mar. 31, 2014
Restricted Stock Units [Member]
 
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of Shares, Beginning Balance 233,763
Number of Shares, Granted 43,803
Number of Shares, Forfeited 0
Number of Shares, Settled (95,997)
Number of Shares, Ending Balance 181,569
Weighted Average Grant Date Fair Value, Beginning Balance $ 87.97
Weighted Average Grant Date Fair Value, Granted $ 183.95
Weighted Average Grant Date Fair Value, Forfeited $ 0
Weighted Average Grant Date Fair Value, Settled $ 61.99
Weighted Average Grant Date Fair Value, Ending Balance $ 124.86