Fair Value Measurements - Estimated Fair Value of Warrant Liability (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares	May 31, 2020 $ / shares	May 22, 2020 USD ($) $ / shares	Apr. 30, 2020 $ / shares	Dec. 31, 2019 USD ($) $ / shares	Jul. 31, 2019 $ / shares	Jul. 23, 2019 USD ($)
Series A Warrants | Stock price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.29	0.29				0.65
Series A Warrants | Strike price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	787.50	787.50				787.50
Series A Warrants | Expected life
Fair Value Assumptions and Methodology for Assets and Liabilities
Weighted-average expected term (years)	1 year 8 months 12 days	1 year 8 months 12 days				2 years 4 months 28 days
Series A Warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	148	148				143.41
Series A Warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.13	0.13				1.62
Series 1 warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Weighted-average expected term (years)							5 years
Series 1 warrants | Stock price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares							1.73
Series 1 warrants | Strike price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares							2.00
Series 1 warrants | Expected life
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability							5.0
Series 1 warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability							109.25
Series 1 warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability							1.83
Series 3 warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Weighted-average expected term (years)			5 years
Series 3 warrants | Stock price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.29	0.29	0.05	0.44
Series 3 warrants | Strike price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.00	0.00	0.44	0.05
Series 3 warrants | Expected life
Fair Value Assumptions and Methodology for Assets and Liabilities
Weighted-average expected term (years)	5 years 1 month 21 days	5 years 1 month 21 days	5 years 6 months	5 years 6 months
Series 3 warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	142	142	141	143
Series 3 warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.28	0.28	0.34	0.34
Underwriter Warrants | Stock price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.29	0.29			2.50	0.65
Underwriter Warrants | Strike price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	52.50	52.50			0.45	52.50
Underwriter Warrants | Expected life
Fair Value Assumptions and Methodology for Assets and Liabilities
Weighted-average expected term (years)	3 years	3 years			4 years 3 months	3 years 9 months 4 days
Underwriter Warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	156	156			141	143.41
Underwriter Warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.16	0.16			0.29	1.69
2019 Bridge Note Warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant								$ 4,259,000
Warrant liability | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	$ 126,000	$ 126,000				$ 3,000
Change in fair value		2,420,000
Warrant liability | Series A Warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	0	0
Warrant liability						0
Change in fair value	0
Warrant liability | Series A Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	0	0				$ 0
Warrant liability | Series 3 warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	123,000	123,000		$ 3,696,000
Change in fair value	2,034,000	2,422,000
Warrant liability | Series 3 warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	125,000	125,000
Warrant liability | Underwriter Warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	1,000	1,000				3,000
Change in fair value	1,000	3,000
Warrant liability | Underwriter Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	$ 1,000	$ 1,000				3,000
Warrant liability | LOC Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant						0
Warrant liability | 2019 Bridge Note Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant						$ 0