Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary shares	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive loss	Treasury Shares
Beginning balance (in shares) at Dec. 31, 2015		41,241				0
Beginning balance at Dec. 31, 2015	$ 69,134	$ 6,331	$ 363,984	$ (278,524)	$ (22,657)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(41,276)			(41,276)
Other comprehensive loss	(908)				(908)
Subscription of warrants	326		326
Exercise of stock options or warrants (in shares)		15
Exercise of stock options or warrants	114	$ 2	112
Vesting of restricted shares (in shares)		115
Vesting of restricted shares	0	$ 18	(18)
Stock-based compensation expense	14,679		14,679
Cross-border merger nominal value adjustment	0	$ (5,937)	5,937
Ending balance (in shares) at Dec. 31, 2016		41,371				0
Ending balance at Dec. 31, 2016	42,069	$ 414	385,020	(319,800)	(23,565)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	68,271			68,271
Other comprehensive loss	299				299
Exercise of stock options or warrants (in shares)		69
Vesting of restricted shares (in shares)		23
Vesting of restricted shares	0
Stock-based compensation expense	8,062		8,062
Exercise of stock options	396		396
Share repurchases (in shares)						2,117
Share repurchases	(22,361)					$ (22,361)
Ending balance (in shares) at Dec. 31, 2017		41,463				2,117
Ending balance at Dec. 31, 2017	85,580	$ 414	393,478	(262,685)	(23,266)	$ (22,361)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment to accumulated deficit (see Note 12: Income Taxes)	(11,156)			(11,156)
Net (loss) income	(95,304)			(95,304)
Other comprehensive loss	(150)				(150)
Exercise of stock options or warrants (in shares)		82
Vesting of restricted shares (in shares)		547
Vesting of restricted shares	0	$ 6	(6)
Stock-based compensation expense	7,852		7,852
Exercise of stock options	$ 535	$ 1	534
Share repurchases (in shares)	5,407					3,290
Share repurchases	$ (27,637)					$ (27,637)
Exercise of warrants (in shares)		603
Exercise of warrants	2,911	$ 6	2,905
Expiration of warrants	2,167		2,167
Employee share purchase plan share issuance (in shares)		25
Employee share purchase plan share issuance	127		127
Equity component of 2023 Notes	26,699		26,699
Ending balance (in shares) at Dec. 31, 2018		42,720				5,407
Ending balance at Dec. 31, 2018	$ 2,780	$ 427	$ 433,756	$ (357,989)	$ (23,416)	$ (49,998)