UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ (DEFICIT) EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary shares	Preferred shares	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive (loss) income	Treasury shares
Beginning balance (in shares) at Dec. 31, 2018		42,720					5,407
Beginning balance at Dec. 31, 2018	$ 2,780	$ 427		$ 433,756	$ (357,989)	$ (23,416)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(13,018)				(13,018)
Other comprehensive income (loss)	213					213
Vesting of restricted shares (in shares)		1
Vesting of restricted shares	0
Employee share purchase plan share issuance (in shares)		42
Employee share purchase plan share issuance	92			92
Stock-based compensation expense	351			351
Ending balance (in shares) at Mar. 31, 2019		42,763					5,407
Ending balance at Mar. 31, 2019	(9,582)	$ 427		434,199	(371,007)	(23,203)	$ (49,998)
Beginning balance (in shares) at Dec. 31, 2018		42,720					5,407
Beginning balance at Dec. 31, 2018	2,780	$ 427		433,756	(357,989)	(23,416)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(30,487)
Ending balance (in shares) at Sep. 30, 2019		42,857					5,407
Ending balance at Sep. 30, 2019	(26,963)	$ 428		434,055	(388,476)	(22,972)	$ (49,998)
Beginning balance (in shares) at Mar. 31, 2019		42,763					5,407
Beginning balance at Mar. 31, 2019	(9,582)	$ 427		434,199	(371,007)	(23,203)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(8,605)				(8,605)
Other comprehensive income (loss)	355					355
Stock-based compensation expense	55			55
Ending balance (in shares) at Jun. 30, 2019		42,763					5,407
Ending balance at Jun. 30, 2019	(17,777)	$ 427		434,254	(379,612)	(22,848)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(8,864)				(8,864)
Other comprehensive income (loss)	(124)					(124)
Vesting of restricted shares (in shares)		82
Vesting of restricted shares		$ 1		(1)
Employee share purchase plan share issuance (in shares)		12
Employee share purchase plan share issuance	31			31
Stock-based compensation expense	(229)			(229)
Ending balance (in shares) at Sep. 30, 2019		42,857					5,407
Ending balance at Sep. 30, 2019	(26,963)	$ 428		434,055	(388,476)	(22,972)	$ (49,998)
Beginning balance (in shares) at Dec. 31, 2019		42,927	0				5,407
Beginning balance at Dec. 31, 2019	(29,199)	$ 429	$ 0	434,391	(391,215)	(22,806)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(865)				(865)
Other comprehensive income (loss)	(821)					(821)
Exercise of stock options (in shares)		146
Exercise of stock options	1,389	$ 2		1,387
February 2020 private placement (in shares)		8,680	488
February 2020 private placement	60,733	$ 87	$ 5	60,641
Vesting of restricted shares (in shares)		19
Vesting of restricted shares	0
Employee share purchase plan share issuance (in shares)		40
Employee share purchase plan share issuance	88			88
Stock-based compensation expense	742			742
Ending balance (in shares) at Mar. 31, 2020		51,812	488				5,407
Ending balance at Mar. 31, 2020	32,067	$ 518	$ 5	497,249	(392,080)	(23,627)	$ (49,998)
Beginning balance (in shares) at Dec. 31, 2019		42,927	0				5,407
Beginning balance at Dec. 31, 2019	(29,199)	$ 429	$ 0	434,391	(391,215)	(22,806)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	18,306
Ending balance (in shares) at Sep. 30, 2020		58,243	488				0
Ending balance at Sep. 30, 2020	171,200	$ 582	$ 5	565,440	(372,909)	(21,918)	$ 0
Beginning balance (in shares) at Mar. 31, 2020		51,812	488				5,407
Beginning balance at Mar. 31, 2020	32,067	$ 518	$ 5	497,249	(392,080)	(23,627)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	30,874				30,874
Other comprehensive income (loss)	1,109					1,109
Exercise of stock options (in shares)		95
Exercise of stock options	393	$ 1		392
February 2020 private placement	(94)			(94)
Employee share purchase plan share issuance	33			33
Stock-based compensation expense	769			769
May 2020 public offering (in shares)		11,630
May 2020 public offering	116,974	$ 116		116,858
Ending balance (in shares) at Jun. 30, 2020		63,537	488				5,407
Ending balance at Jun. 30, 2020	182,125	$ 635	$ 5	615,207	(361,206)	(22,518)	$ (49,998)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(11,703)				(11,703)
Other comprehensive income (loss)	600					600
Exercise of stock options (in shares)		22
Exercise of stock options	47			47
February 2020 private placement	(69)			(69)
Vesting of restricted shares (in shares)		82
Vesting of restricted shares	0	$ 1		(1)
Employee share purchase plan share issuance (in shares)		9
Employee share purchase plan share issuance	56			56
Stock-based compensation expense	194			194
May 2020 public offering	(50)			(50)
Retirement of treasury shares (in shares)		(5,407)					(5,407)
Ending balance (in shares) at Sep. 30, 2020		58,243	488				0
Ending balance at Sep. 30, 2020	$ 171,200	$ 582	$ 5	$ 565,440	$ (372,909)	$ (21,918)	$ 0