Summary of Significant Accounting Policies (Tables)
 6 Months Ended
Jun. 30, 2018
Accounting Policies [Abstract]  
Anti-dilutive shares
   

June 30,

2018

    

December 31,

2017

  
Options to purchase common stock     978,911       940,121  
Warrants to purchase common stock     2,288,141       2,268,141  
Potential equivalent shares excluded     3,267,052       3,208,262