Fair Value Measurements - Estimated Fair Value of Warrant Liability (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares	Jun. 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	0.49	0.49				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 10 months 24 days	1 year 10 months 24 days				2 years 4 months 28 days
Series A Warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	141.00	141.00				143.41
Series A Warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.16	0.16				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	0.49	0.49	0.05	0.44
Series 3 warrants | Strike price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.05	0.05	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 4 months 21 days	5 years 4 months 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	141	141	141	143
Series 3 warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.29	0.29	0.34	0.34
Underwriter Warrants | Stock price
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability | $ / shares	0.49	0.49			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 months 18 days	3 years 3 months 18 days			4 years 3 months	3 years 9 months 4 days
Underwriter Warrants | Volatility
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	141	141			141	143.41
Underwriter Warrants | Risk free rate
Fair Value Assumptions and Methodology for Assets and Liabilities
Warrant liability	0.18	0.18			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	$ 4,086,000	$ 4,086,000				$ 3,000
Change in fair value		387,000
Warrant liability | Series A Warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	1	1
Warrant liability						10
Change in fair value	2	9
Warrant liability | Series A Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	1	1				$ 10
Warrant liability | Series 3 warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	4,084,478	4,084,478		$ 3,695,723
Change in fair value	386,755	386,755
Warrant liability | Series 3 warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	4,084,478	4,084,478
Warrant liability | Underwriter Warrants
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	1,566	1,566				3,482
Change in fair value	530	735
Warrant liability | Underwriter Warrants | Recurring | Level 3
Fair Value Assumptions and Methodology for Assets and Liabilities
Fair value of warrant	$ 1,566	$ 1,566				3,482
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