Annual report pursuant to Section 13 and 15(d)

Fair Value Measurement - Summary of Changes in Fair Value of Level 3 Financial Liabilities on Recurring Basis (Details)

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Fair Value Measurement - Summary of Changes in Fair Value of Level 3 Financial Liabilities on Recurring Basis (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Gain on revaluation of warrants issued in December 2019, May 2019 financing, and December 2015 financing $ (6,376,000) $ (1,063,000)
Loss on modification of 2015 Warrants 257,000 0
Warrant Liability    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 585,000  
Initial fair value of warrants issued in conjunction with May 2019 financing 7,334,000  
Initial fair value of warrants issued in conjunction with December 2019 financing 2,507,000  
Gain on revaluation of warrants issued in December 2019, May 2019 financing, and December 2015 financing (6,376,000)  
Loss on modification of 2015 Warrants 257,000  
Gain on revaluation of contingent liabilities 0  
Ending balance 4,307,000 585,000
Contingent Success Fee Liability    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 34,000  
Initial fair value of warrants issued in conjunction with May 2019 financing 0  
Initial fair value of warrants issued in conjunction with December 2019 financing 0  
Gain on revaluation of warrants issued in December 2019, May 2019 financing, and December 2015 financing 0  
Loss on modification of 2015 Warrants 0  
Gain on revaluation of contingent liabilities 28,000  
Ending balance $ 6,000 $ 34,000