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	11				11
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	87,054	$ 420	427,383	(274,921)	(23,255)	$ (42,573)
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	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)