Consolidated Statements of Shareholders' (Deficit) 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, 2016		41,371				0
Beginning 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 income (loss)	299				299
Exercise of stock options (in shares)		69
Exercise of stock options	396		396
Vesting of restricted shares (in shares)		23
Vesting of restricted shares	0
Share-based compensation expense	8,062		8,062
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 13: Income Taxes)	(11,156)			(11,156)
Net (loss) income	(95,304)			(95,304)
Other comprehensive income (loss)	(150)				(150)
Exercise of stock options (in shares)		82
Exercise of stock options	535	$ 1	534
Exercise of warrants (in shares)		603
Exercise of warrants	2,911	$ 6	2,905
Expiration of warrants	2,167		2,167
Vesting of restricted shares (in shares)		547
Vesting of restricted shares	0	$ 6	(6)
Employee share purchase plan share issuance (in shares)		25
Employee share purchase plan share issuance	127		127
Share-based compensation expense	7,852		7,852
Equity component of 2023 Notes	26,699		26,699
Share repurchases (in shares)						3,290
Share repurchases	(27,637)					$ (27,637)
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(33,226)			(33,226)
Other comprehensive income (loss)	$ 610				610
Exercise of stock options (in shares)	0
Vesting of restricted shares (in shares)		153
Vesting of restricted shares	$ 0	$ 2	(2)
Employee share purchase plan share issuance (in shares)		54
Employee share purchase plan share issuance	118		118
Share-based compensation expense	$ 519		519
Share repurchases (in shares)	5,407
Ending balance (in shares) at Dec. 31, 2019		42,927				5,407
Ending balance at Dec. 31, 2019	$ (29,199)	$ 429	$ 434,391	$ (391,215)	$ (22,806)	$ (49,998)