Share-Based Payments - 2019 Inducement Share Incentive Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 12, 2019
Weighted average exercise price in $ per share
Share-based compensation expense	$ 5,219,000	$ 9,748,000	$ 5,154,000
Fair Value Assumptions
Weighted-average remaining contractual life	8 years 8 months 12 days
2019 Inducement Plan
Options
Outstanding at beginning of year (in shares)	60,565
Granted (in shares)	18,200	70,315
Forfeited (in shares)	(52,950)	(9,750)
Outstanding at end of year (in shares)	25,815	60,565
Vested and exercisable at end of year (in shares)	4,396
Weighted average exercise price in $ per share
Outstanding balance at beginning of year (in dollars per share)	$ 21.45
Granted (in dollars per share)	13.50	$ 22.20
Forfeited (in dollars per share)	19.59	26.92
Outstanding balance at end of year (in dollars per share)	19.04	$ 21.45
Vested and exercisable balance at end of year (in dollars per share)	$ 26.96
Share-based compensation expense	$ 38,000,000	$ 77,000
Weighted-average grant date fair value (in dollars per share)	$ 7.93
Unrecognized compensation expense
Exercise price minimum range	13.50
Exercise price maximum range	$ 29.90
2019 Inducement Plan | Ordinary Shares
Share-Based Payments
Shares reserved for future issuance				200,000
2019 Inducement Plan | Stock Options
Weighted average exercise price in $ per share
Weighted-average grant date fair value (in dollars per share)		$ 13.04
Fair Value Assumptions
Expected term of options (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Unrecognized compensation expense
Total unrecognized compensation related to unvested options	$ 200,000
Recognition period	1 year 2 months 12 days
2019 Inducement Plan | Stock Options | Minimum
Fair Value Assumptions
Expected volatility (as a percent)	63.70%	59.80%
Risk-free interest rate (as a percent)	0.96%	2.55%
2019 Inducement Plan | Stock Options | Maximum
Fair Value Assumptions
Expected volatility (as a percent)	64.00%	61.40%
Risk-free interest rate (as a percent)	1.37%	3.03%