Share-Based Payments - 2019 Inducement Share Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 12, 2019
Fair Value Assumptions
Expected volatility (as a percent)			77.30%
Expected term of options (in years)			5 years 6 months
Risk-free interest rate (as a percent)			1.00%
Minimum
Fair Value Assumptions
Expected volatility (as a percent)			75.30%
Risk-free interest rate (as a percent)			1.02%
Maximum
Fair Value Assumptions
Expected volatility (as a percent)			76.30%
Risk-free interest rate (as a percent)			1.16%
Stock Options
Weighted average exercise price in $ per share
Share-based compensation expense	$ 100	$ 51	$ 200	$ 65
2019 Inducement Plan
Options
Outstanding at beginning of year (in shares)			25,815
Forfeited (in shares)			(13,053)
Outstanding at end of year (in shares)	12,762		12,762
Vested and exercisable at end of year (in shares)	8,510		8,510
Weighted average exercise price in $ per share
Outstanding balance at beginning of year (in dollars per share)			$ 19.04
Forfeited (in dollars per share)			18.20
Outstanding balance at end of year (in dollars per share)	$ 19.90		19.90
Vested and exercisable balance at end of year (in dollars per share)	$ 19.16		$ 19.16
Share-based compensation expense	$ 7		$ 23	$ 100
2019 Inducement Plan | Ordinary Shares
Share-Based Payments
Shares reserved for future issuance					200,000
2019 Inducement Plan | Stock Options
Fair Value Assumptions
Weighted-average remaining contractual life			8 years 2 months 12 days
Unrecognized compensation expense
Total unrecognized compensation related to unvested options	$ 53		$ 53
Recognition period			2 years