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Stockholder Protection Rights Plan (Details)
12 Months Ended
Dec. 31, 2017
Right
$ / shares
Dec. 16, 2016
$ / shares
Dec. 15, 2016
$ / shares
Stockholder Protection Rights Plan [Abstract]      
Number of right for each outstanding share | Right 1    
Proportion of right entitles to purchase series A preferred stock 0.0001    
Exercise price of warrants (in dollars per share) | $ / shares $ 30 $ 3.06 $ 4.20
Number of business days after announcement rights are not exercisable for certain persons 10 days    
Beneficial ownership percentage of company outstanding shares of common stock by acquiring person 15.00%    
Percentage of company outstanding shares of common stock by acquiring person 50.00%