Fair Value of Financial Instruments - Fair value of the warrants (Details) $ in Thousands		12 Months Ended
	Jun. 07, 2019	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Reverse stock split	0.167		0.167
Warrant liability, measurement input		17.00
Warrants to purchase (in shares) | shares		49,997
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital | $		$ 503
Expected life		3 years 2 months 1 day	3 years 7 months 21 days
Exercise price (1)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input			14.46
Stock price (2)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input			13.20
Volatility (3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		83.61	83.7
Risk-free interest rate (4)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		1.69	2.50
Expected dividend
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant liability, measurement input		0.00