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Equity Financings and Warrants - Summary of Warrants by Year of Expiration (Details)
 6 Months Ended
Jun. 30, 2019
$ / shares
shares
Class Of Warrant Or Right [Line Items]  
Number of Warrants | shares 135,862
Weighted Average Exercise Price | $ / shares $ 113.04
2020  
Class Of Warrant Or Right [Line Items]  
Year of Expiration 2020
Number of Warrants | shares 2,461
Weighted Average Exercise Price | $ / shares $ 287.28
2022  
Class Of Warrant Or Right [Line Items]  
Year of Expiration 2022
Number of Warrants | shares 133,401
Weighted Average Exercise Price | $ / shares $ 109.80