Warrants - Warrant assumptions (Details)	Dec. 31, 2019 Y shares	Nov. 12, 2019 Y shares	Dec. 31, 2018 shares	Nov. 30, 2018 shares	Dec. 31, 2017 shares
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares	13,609,929		127,540		57
Series A warrants
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares				66,667
Series A warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares		3,333,333
Series E warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares		3,333,334
Series F warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares		3,264,167
June 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares		233,334
September 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares) | shares		233,334
Strike Price | Series A warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	2.64
Strike Price | Series A warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		2.64
Strike Price | Series B warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	2.40
Strike Price | Series E warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	6.00
Strike Price | Series E warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		6.00
Strike Price | Series F warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	0.12
Strike Price | Series F warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		0.12
Strike Price | June 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		3.00
Strike Price | September 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		6.00
Expected volatility | Series A warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	164.1
Expected volatility | Series A warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		93.5
Expected volatility | Series B warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	164.1
Expected volatility | Series E warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	93.2
Expected volatility | Series E warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		93.5
Expected volatility | Series F warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	93.2
Expected volatility | Series F warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		93.5
Expected volatility | June 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		93.5
Expected volatility | September 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		93.5
Expected term | Series A warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	5.22
Expected term | Series A warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		5.1
Expected term | Series B warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	1.22
Expected term | Series E warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	5.11
Expected term | Series E warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		5.1
Expected term | Series F warrants | Monte Carlo Simulation Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)	5.11
Expected term | Series F warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		5.1
Expected term | June 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		4.7
Expected term | September 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		4.9
Risk-free interest rate | Series A warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		1.73
Risk-free interest rate | Series E warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		1.73
Risk-free interest rate | Series F warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		1.73
Risk-free interest rate | June 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		1.73
Risk-free interest rate | September 2019 placement agent warrants | Black Scholes Model
Class of Warrant or Right [Line Items]
Warrant fair value measurement inputs (as a percent)		1.73