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Stockholders' Equity - Summary of Anti-Dilutive Options Excluded (Details) - $ / shares
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Stockholders' Equity Note [Abstract]    
Options to purchase shares of common stock (in shares) 3,204,951 2,661,571
Weighted average exercise price of options (in dollars per share) $ 50.83 $ 50.89