Stockholders' Equity (Details) - USD ($)		1 Months Ended							12 Months Ended
	Jan. 01, 2022	Jan. 31, 2022	Sep. 30, 2021	May 31, 2021	Mar. 31, 2021	Dec. 31, 2020	May 31, 2020	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stockholders' Equity
Net proceeds for deducting commissions and offering expenses payable									$ 42,280,000	$ 7,520,000	$ 27,945,000
Shares issued									$ 70,138,000	$ 61,060,000	$ 48,082,000
Nominal value						$ 0.01			$ 0.01	$ 0.01
Regular purchase			$ 2,500,000
Public offering
Stockholders' Equity
Number of shares issued						6,000,000
Shares issued, price per share						$ 2.50				$ 2.50
Net proceeds for deducting commissions and offering expenses payable						$ 15,000,000.0
Net proceeds from sale of stock						$ 13,300,000
Purchase agreement
Stockholders' Equity
Number of shares issued							4,144,537
Number of ordinary shares that can be purchased by warrant holders							4,144,537
Share and warrant price							$ 9.1686
Net proceeds for deducting commissions and offering expenses payable							$ 38,000,000.0
Net proceeds from sale of stock							$ 35,200,000
Jefferies LLC | At-the-market offering | Maximum
Stockholders' Equity
Net proceeds for deducting commissions and offering expenses payable		$ 19,000,000.0
Purchasers | Warrants Issued In May 2020
Stockholders' Equity
Warrants outstanding									4,059,532
Purchasers | Purchase agreement
Stockholders' Equity
Number of shares issued					9,761,010			1,379,310
Number of ordinary shares that can be purchased by warrant holders					4,880,505			1,379,310			1,379,310
Share and warrant price								$ 14.50
Per share exercise price of right									$ 2.39
Term					5 years
Net proceeds for deducting commissions and offering expenses payable								$ 20,000,000.0
Net proceeds from sale of stock					$ 23,400,000			$ 18,300,000
Proceeds from Issuance or Sale of Equity					$ 25,400,000
Nominal value					$ 0.01
Warrants outstanding									5,180,505
Purchasers | Purchase agreement | Warrants Issued In December 2019
Stockholders' Equity
Per share exercise price of right									$ 19.00
Term									3 years 6 months
Warrants outstanding									1,379,310
Purchasers | Purchase agreement | Warrants Issued In May 2020
Stockholders' Equity
Per share exercise price of right									$ 7.92
Term									2 years
Purchasers | Purchase agreement | Ordinary Share Warrants
Stockholders' Equity
Number of ordinary shares that can be purchased by warrant holders					600,000
Share and warrant price					$ 2.4525
Per share exercise price of right					$ 2.39
Purchasers | Purchase agreement | Pre-Funded Warrants
Stockholders' Equity
Number of ordinary shares that can be purchased by warrant holders					300,000
Share and warrant price					$ 2.4425
Per share exercise price of right					$ 0.01
Lincoln Park Capital Fund, LLC | Purchase agreement
Stockholders' Equity
Net proceeds for deducting commissions and offering expenses payable		19,000,000.0
Net proceeds from sale of stock		$ 1,600,000							$ 2,400,000
Lincoln Park Capital Fund, LLC | Purchase agreement | Ordinary shares
Stockholders' Equity
Number of shares issued	3,600,000	3,600,000							2,400,000
Net proceeds for deducting commissions and offering expenses payable	$ 1,600,000								$ 2,400,000
Commitment shares			632,474
Commitment share price			$ 0.01
Regular purchase			$ 2,500,000
Lincoln Park Capital Fund, LLC | Purchase agreement | Ordinary shares | Maximum
Stockholders' Equity
Net proceeds for deducting commissions and offering expenses payable	$ 19,000,000.0
Shares issued			$ 23,000,000.0
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $0.25 Per Share | Ordinary shares
Stockholders' Equity
Share price			$ 0.25
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $0.25 Per Share | Ordinary shares | Maximum
Stockholders' Equity
Number of shares issued			400,000
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $2.00 Per Share | Ordinary shares
Stockholders' Equity
Share price			$ 2.00
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $2.00 Per Share | Ordinary shares | Maximum
Stockholders' Equity
Number of shares issued			600,000
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $3.00 Per Share | Ordinary shares
Stockholders' Equity
Share price			$ 3.00
Lincoln Park Capital Fund, LLC | Purchase agreement | Share Price Not Below $3.00 Per Share | Ordinary shares | Maximum
Stockholders' Equity
Number of shares issued			800,000
Open Market Sale Agreement | Jefferies LLC | Ordinary shares
Stockholders' Equity
Number of shares issued	1,338,282			5,925,699					18,232,689
Net proceeds for deducting commissions and offering expenses payable	$ 595,000			$ 31,900,000					$ 29,300,000
Net proceeds from sale of stock	$ 580,000
Aggregate gross sale proceeds for ordinary shares				$ 33,700,000					$ 30,500,000
Nominal value				$ 0.01
Ordinary shares remained unsold				$ 16,300,000
Open Market Sale Agreement | Jefferies LLC | Ordinary shares | Maximum
Stockholders' Equity
Net proceeds for deducting commissions and offering expenses payable				50,000,000.0
Aggregate gross sale proceeds for ordinary shares				$ 50,000,000.0