Warrants - Summary of Assumptions to Use Option Pricing Model (Details)	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2018	Jan. 31, 2017	Sep. 30, 2016
2018 Direct Registered Offering | Expected term (in years)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs			7.0
2018 Direct Registered Offering | Expected volatility (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs			0.625
2018 Direct Registered Offering | Risk-free interest rate (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs			0.028
2018 Direct Registered Offering | Expected dividend yield (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs			0
2017 Placement Warrants Liability | Expected term (in years)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	2.0	3.0		7.0
2017 Placement Warrants Liability | Expected volatility (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0.860	0.869		0.629
2017 Placement Warrants Liability | Risk-free interest rate (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0.004	0.002		0.022
2017 Placement Warrants Liability | Expected dividend yield (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0	0		0
2016 Placement Warrants Liability | Expected term (in years)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	1.6	2.6			7.0
2016 Placement Warrants Liability | Expected volatility (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0.855	0.863			0.616
2016 Placement Warrants Liability | Risk-free interest rate (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0.003	0.002			0.014
2016 Placement Warrants Liability | Expected dividend yield (%)
Fair Value Inputs1 Liabilities Quantitative Information [Line Items]
Warrants, fair value measurement inputs	0	0			0