Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Beginning Balance at Dec. 31, 2018	$ 31	$ 69,970	$ 448,731	$ (33,650)		$ 138,139
Shares issued upon exercise of stock options		2,251
Net income			18,894			6,084	$ 24,978
Dividends			(8,649)
Share-based compensation (adjustment)		350	353			321
Purchase of subsidiary shares from noncontrolling interest		(468)				(376)
Transfer of subsidiary shares purchased
Foreign currency translation adjustment, net of tax				(6,304)		(2,241)
Transfer from other comprehensive income into earnings				(136)
Net derivative instrument loss, net of tax				(7)		(52)	(52)
End Balance at Mar. 31, 2019		72,103	459,329	(40,097)	$ (37,475)	141,875	595,766
Beginning Balance at Dec. 31, 2019	$ 31	70,664	474,637	(39,853)		140,994	608,998
Shares issued upon exercise of stock options		641
Net income			10,059			3,240	13,299
Dividends			(10,406)			(324)
Share-based compensation (adjustment)		427	(343)			(34)
Purchase of subsidiary shares from noncontrolling interest
Transfer of subsidiary shares purchased		1,886				(139)
Foreign currency translation adjustment, net of tax				(8,392)		(3,529)
Transfer from other comprehensive income into earnings				(52)
Net derivative instrument loss, net of tax				200		57	57
End Balance at Mar. 31, 2020		$ 73,618	$ 473,947	$ (48,097)	$ (37,475)	$ 140,265	$ 602,289