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Stockholders' Equity - Summary of Anti-Dilutive Options Excluded (Details) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Stockholders' Equity Note [Abstract]        
Options to purchase shares of common stock 1,313,261 1,578,804 1,263,599 735,675
Weighted average exercise price of options $ 54.00 $ 49.43 $ 54.00 $ 54.00