Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Director	Employee	Common stock	Common stock Director	Common stock Employee	Paid-in capital	Paid-in capital Employee	Retained earnings	Accumulated other comprehensive loss
Beginning Balance (in shares) at Dec. 31, 2016					14,556,000
Balance at beginning of year at Dec. 31, 2016		$ 197,728			$ 146			$ 173,600		$ 60,981	$ (36,999)
Comprehensive income (loss):
Net (loss) income		2,154								2,154
Translation adjustment		7,823									7,823
Derivative fair value adjustment		17									17
Effect of retirement benefit obligations		(166)									(166)
Comprehensive (loss) income		9,828
Restricted shares issued to directors (in shares)						30,000
Restricted shares issued to directors			$ 0
Net issuance of restricted shares to employees (in shares)							97,000
Net issuance of restricted shares to employees				$ 2			$ 1		$ 1
Stock compensation expense		$ 3,390						3,390
Net exercise of stock options (in shares)		300,000			254,000
Net exercise of stock options		$ 2,537			$ 2			2,535
Shares effectively repurchased for required employee withholding taxes (in shares)					(34,000)
Shares effectively repurchased for required employee withholding taxes		(694)						(694)
Adoption of ASU 2016-09		31						77		(46)
Dividends	[1]	(2,543)								(2,543)
Ending Balance (in shares) at Dec. 31, 2017					14,903,000
Balance at end of year at Dec. 31, 2017		210,279			$ 149			178,909		60,546	(29,325)
Comprehensive income (loss):
Net (loss) income		(1,720)								(1,720)
Translation adjustment		(5,906)									(5,906)
Derivative fair value adjustment		147									147
Effect of retirement benefit obligations		468									468
Comprehensive (loss) income		$ (7,011)
Restricted shares issued to directors (in shares)						46,000
Net issuance of restricted shares to employees (in shares)							211,000
Net issuance of restricted shares to employees				$ 0			$ 2		(2)
Issuance of 5,593,116 shares of common stock for acquisition of Filament, net of equity issuance costs (in shares)		5,593,116			5,593,000
Issuance of 5,593,116 shares of common stock for acquisition of Filament, net of equity issuance costs		$ 75,970			$ 56			75,914
Stock compensation expense		$ 4,091						4,091
Net exercise of stock options (in shares)		58,000			58,000
Net exercise of stock options		$ 286			$ 1			285
Shares effectively repurchased for required employee withholding taxes (in shares)					(47,000)
Shares effectively repurchased for required employee withholding taxes		(560)						(560)
Dividends	[1]	(3,562)								(3,562)
Ending Balance (in shares) at Dec. 31, 2018					20,764,000
Balance at end of year at Dec. 31, 2018		279,493			$ 208			258,637		55,264	(34,616)
Comprehensive income (loss):
Net (loss) income		(44,415)								(44,415)
Translation adjustment		(292)									(292)
Derivative fair value adjustment		1,003									1,003
Effect of retirement benefit obligations		(550)									(550)
Comprehensive (loss) income		(44,254)
Net issuance of restricted shares to employees (in shares)							416,000
Net issuance of restricted shares to employees							$ 4		(4)
Performance shares issued to employees (in shares)							67,000
Performance shares issued to employees							$ 1		$ (1)
Stock compensation expense		$ 5,021						5,021
Net exercise of stock options (in shares)		75,000			53,000
Net exercise of stock options		$ 132			$ 1			131
Shares effectively repurchased for required employee withholding taxes (in shares)					(44,000)
Shares effectively repurchased for required employee withholding taxes		(399)			$ (1)			(398)
Dividends	[1]	(3,676)								(3,676)
Ending Balance (in shares) at Dec. 31, 2019					21,256,000
Balance at end of year at Dec. 31, 2019		$ 236,317			$ 213			$ 263,386		$ 7,173	$ (34,455)

[1] Cash dividend declared per share of common stock, were $0.17, $0.17 and $0.17 in 2017, 2018 and 2019, respectively.