Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2017	$ 269	$ 294,613	$ (201,541)	$ (5,712)	$ 87,629
Exercise of share options	2	82			84
Share-based compensation expense		1,824			1,824
Tax on vesting of restricted share units		(156)			(156)
Other comprehensive income (loss),				557	557
Net income (loss)			(10,326)		(10,326)
Balance at Mar. 31, 2018	271	296,363	(211,867)	(5,155)	79,612
Balance at Dec. 31, 2017	269	294,613	(201,541)	(5,712)	87,629
Other comprehensive income (loss),					(1,578)
Net income (loss)					(20,281)
Balance at Sep. 30, 2018	276	300,802	(221,822)	(7,290)	71,966
Balance at Mar. 31, 2018	271	296,363	(211,867)	(5,155)	79,612
Exercise of share options	1	729			730
Share-based compensation expense		922			922
Tax on vesting of restricted share units		(108)			(108)
Other comprehensive income (loss),				(1,521)	(1,521)
Net income (loss)			(6,471)		(6,471)
Balance at Jun. 30, 2018	272	297,906	(218,338)	(6,676)	73,164
Exercise of share options	4	1,881			1,885
Share-based compensation expense		1,015			1,015
Other comprehensive income (loss),				(614)	(614)
Net income (loss)			(3,484)		(3,484)
Balance at Sep. 30, 2018	276	300,802	(221,822)	(7,290)	71,966
Balance at Dec. 31, 2018	276	303,015	(80,762)	(8,523)	214,006
Exercise of share options	2	1,800			1,802
Share-based compensation expense		845			845
Tax on vesting of restricted share units		(145)			(145)
Other comprehensive income (loss),				1,167	1,167
Net income (loss)			(1,496)		(1,496)
Balance at Mar. 31, 2019	278	305,515	(82,258)	(7,356)	216,179
Balance at Dec. 31, 2018	276	303,015	(80,762)	(8,523)	214,006
Other comprehensive income (loss),					(1,902)
Net income (loss)					(189)
Balance at Sep. 30, 2019	278	306,601	(81,485)	(10,425)	214,969
Balance at Mar. 31, 2019	278	305,515	(82,258)	(7,356)	216,179
Exercise of share options	2	1,531			1,533
Share-based compensation expense		846			846
Tax on vesting of restricted share units		(10)			(10)
Other comprehensive income (loss),				(1,355)	(1,355)
Net income (loss)			590		590
Balance at Jun. 30, 2019	280	307,882	(81,668)	(8,711)	217,783
Exercise of share options		593			593
Share-based compensation expense		983			983
Tax on vesting of restricted share units		(68)			(68)
Other comprehensive income (loss),				(1,714)	(1,714)
Net income (loss)			717		717
Ordinary shares repurchased	(2)	(2,789)	(534)		(3,325)
Balance at Sep. 30, 2019	$ 278	$ 306,601	$ (81,485)	$ (10,425)	$ 214,969