Warrant Liability - Weighted-average key assumptions (Details)	Mar. 03, 2020	Jan. 07, 2020	Dec. 31, 2019
January 2020 Private Placement Warrant \| Expected volatility
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	124	121
January 2020 Private Placement Warrant \| Risk-free interest rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	0.8	1.6
January 2020 Private Placement Warrant \| Expected term (in years)
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	4.9	5.0
January 2020 Private Placement Warrant \| Weighted-average fair value per share warrant
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	7.80	5.70
August 2019 Placement Warrants \| Expected volatility
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	124		125
August 2019 Placement Warrants \| Risk-free interest rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	0.8		1.7
August 2019 Placement Warrants \| Expected term (in years)
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	4.5		4.6
August 2019 Placement Warrants \| Weighted-average fair value per share warrant
Class of Warrant or Right [Line Items]
Warrants and rights outstanding	6.30		3.30