Equity Instruments and Transactions (Details) - USD ($)			1 Months Ended		12 Months Ended
	Apr. 28, 2020	Feb. 21, 2020	Aug. 31, 2020	Feb. 29, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Ordinary shares, shares authorized (in shares)					500,000,000	500,000,000
Ordinary shares, nominal value (in usd per share)				$ 0.01	$ 0.01	$ 0.01
Ordinary shares, shares issued (in shares)					58,396,000	42,927,000
Ordinary shares, shares outstanding (in shares)					58,396,000	37,520,000
Preferred shares, shares authorized (in shares)					50,000,000	50,000,000
Preferred shares, nominal value (in usd per share)				$ 0.01	$ 0.01	$ 0.01
Preferred shares, shares issued (in shares)					488,000	0
Preferred shares, shares outstanding (in shares)					488,000	0
Maximum aggregate offering price of securities under shelf registration				$ 250,000
Maximum aggregate offering price of ADSs under shelf registration				50,000
Transaction costs				$ 428,000
Prepaid expenses and other current assets					$ 38,726,000	$ 4,264,000
February 2020 private placement					60,570,000
Proceeds from the February 2020 private placement					60,570,000	$ 0	$ 0
Maximum threshold percentage for trigger of convertible preferred stock		9.99%
Retirement of treasury shares (in shares)			5,407,000
Retirement of treasury shares					0
Securities Purchase Agreement
Class of Stock [Line Items]
February 2020 private placement		$ 65,000,000
Proceeds from the February 2020 private placement		$ 60,570,000
Securities Purchase Agreement | American Depositary Receipts
Class of Stock [Line Items]
Stock issued during period, new issues (in shares)		8,680,000
Securities Purchase Agreement | Series A Preferred Stock
Class of Stock [Line Items]
Stock issued during period, new issues (in shares)		488,000
Shares issued, price per share (in dollars per share)		$ 7.09
Public Offering | American Depositary Shares
Class of Stock [Line Items]
Public offering, shares issued	11,630,000
Public offering, price per share (in dollars per share)	$ 10.75
Public offering, proceeds	$ 125,000,000
Net proceeds from public offering	$ 116,924,000
Additional paid-in capital
Class of Stock [Line Items]
Charges against additional paid-in capital					214,000
Prepaid expenses and other current assets					214,000
February 2020 private placement					60,478,000
Issuance costs recorded as a reduction to additional paid-in capital		$ 4,430,000
Retirement of treasury shares			$ 49,944,000		$ 49,944,000
Treasury Shares
Class of Stock [Line Items]
Retirement of treasury shares (in shares)					5,407,000
Retirement of treasury shares			49,998,000		$ 49,998,000
Ordinary shares
Class of Stock [Line Items]
February 2020 private placement					$ 87,000
Stock issued during period, new issues (in shares)					8,680,000
Retirement of treasury shares (in shares)					5,407,000
Retirement of treasury shares			$ 54,000		$ 54,000