Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Foreign Currency Translation	Minimum Benefit Retirement Liability	Retained Earnings	Non-controlling Interest	Total
Beginning Balance at Dec. 31, 2018	$ 38	$ 97,418	$ (590)	$ (2,859)	$ 512,783	$ 512	$ 607,302
Beginning Balance (in shares) at Dec. 31, 2018	38,164,000
Stock issued from equity plans		(1,707)					(1,707)
Stock issued from equity plans (in shares)	72,000
Stock-based compensation		3,199					3,199
Foreign currency translation			(1,975)				(1,975)
Minimum benefit retirement liability				(53)			(53)
Net income					15,370	8	15,378
Comprehensive income			(1,975)	(53)	15,370	8	13,350
Ending Balance at Mar. 31, 2019	$ 38	98,910	(2,565)	(2,912)	528,153	520	622,144
Ending Balance (in shares) at Mar. 31, 2019	38,236,000
Adoption of new accounting standards					(102)		(102)
Beginning Balance at Dec. 31, 2019	$ 38	104,849	(3,113)	(2,784)	577,724	546	$ 677,260
Beginning Balance (in shares) at Dec. 31, 2019	38,358,000						38,358,000
Stock issued from equity plans		(2,171)					$ (2,171)
Stock issued from equity plans (in shares)	64,000
Stock-based compensation		3,048					3,048
Stock buyback		(7,248)					(7,248)
Stock buyback (in shares)	(170,000)
Foreign currency translation			(3,061)				(3,061)
Minimum benefit retirement liability				154			154
Net income					18,063	15	18,078
Comprehensive income							15,171
Ending Balance at Mar. 31, 2020	$ 38	$ 98,478	$ (6,174)	$ (2,630)	$ 595,685	$ 561	$ 685,958
Ending Balance (in shares) at Mar. 31, 2020	38,252,000						38,252,000