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Marketable Securities and Fair Value Measurements - Narrative (Details) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Jul. 01, 2015
Mar. 31, 2012
Marketable Securities and Fair Value Measurements (Textual) [Abstract]              
Carryover basis           $ 0  
Stock warrants exercised (shares)     0 0      
Common stock warrants $ 940,341   $ 940,341   $ 1,167,614    
Increase/decrease in fair value included in change in fair value of common stock warrants $ (423,000) $ (3,000) $ (227,000) $ 511,000      
Using Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]              
Marketable Securities and Fair Value Measurements (Textual) [Abstract]              
Number of shares held in an affiliated entity (shares) 1,644,155   1,644,155   1,644,155    
Using Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Common Stock [Member]              
Marketable Securities and Fair Value Measurements (Textual) [Abstract]              
Investment owned (shares) 395,758   395,758        
Using Significant Unobservable Inputs (Level 3) [Member]              
Marketable Securities and Fair Value Measurements (Textual) [Abstract]              
Increase/decrease in fair value included in change in fair value of common stock warrants     $ (227,273)        
Using Significant Unobservable Inputs (Level 3) [Member] | Second warrant [Member]              
Marketable Securities and Fair Value Measurements (Textual) [Abstract]              
Common stock purchase warrant (shares)             150,000