UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ (DEFICIT) EQUITY Statement - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary shares	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive (loss) income	Treasury Shares
Beginning balance (in shares) at Dec. 31, 2017		41,463				2,117
Beginning balance at Dec. 31, 2017	$ 85,580	$ 414	$ 393,478	$ (262,685)	$ (23,266)	$ (22,361)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(12,236)			(12,236)
Other comprehensive income (loss)	(404)				(404)
Stock-based compensation expense	2,134		2,134
Exercise of warrants (in shares)		603
Exercise of warrants	2,911	$ 6	2,905
Expiration of warrants	2,167		2,167
Equity component of 2023 Notes	26,699		26,699
Share repurchases (in shares)						2,307
Share repurchases	(20,212)					$ (20,212)
Ending balance (in shares) at Mar. 31, 2018		42,066				4,424
Ending balance at Mar. 31, 2018	86,639	$ 420	427,383	(274,921)	(23,670)	$ (42,573)
Beginning balance (in shares) at Dec. 31, 2017		41,463				2,117
Beginning balance at Dec. 31, 2017	85,580	$ 414	393,478	(262,685)	(23,266)	$ (22,361)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(15,674)
Ending balance (in shares) at Jun. 30, 2018		42,148				5,407
Ending balance at Jun. 30, 2018	78,546	$ 421	430,141	(278,359)	(23,659)	$ (49,998)
Beginning balance (in shares) at Mar. 31, 2018		42,066				4,424
Beginning balance at Mar. 31, 2018	86,639	$ 420	427,383	(274,921)	(23,670)	$ (42,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(3,438)			(3,438)
Other comprehensive income (loss)	11				11
Stock-based compensation expense	2,224		2,224
Exercise of warrants (in shares)		82
Exercise of warrants	535	$ 1	534
Share repurchases (in shares)						983
Share repurchases	(7,425)					$ (7,425)
Ending balance (in shares) at Jun. 30, 2018		42,148				5,407
Ending balance at Jun. 30, 2018	78,546	$ 421	430,141	(278,359)	(23,659)	$ (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	(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	(21,623)
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)
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	(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)