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Share-Based Compensation - Summary of Transactions of the Company's Restricted Stock (Details) - Restricted Stock - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2013
Restricted Stock    
Units outstanding at the beginning of the period 400,000  
Units granted 300,000 100,000.0
Units vested (100,000)  
Units forfeited 0  
Units outstanding at the end of the period 600,000  
Weighted Average Grant Date Value    
Units outstanding at the beginning of the period (in dollars per share) $ 182.83  
Units granted 197.59  
Units vested 174.19  
Units forfeited 190.23  
Units outstanding at the end of the period (in dollars per share) $ 192.04