CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Balance, beginning at Dec. 31, 2016	$ 31	$ 63,103	$ 402,714	$ (57,982)	$ (37,475)	$ 113,267	$ 483,658
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options		542					542
Net income			13,373			4,794	18,167
Dividends			(5,299)				(5,299)
Share based compensation		234	169			121	524
Foreign currency translation adjustment, net of tax				4,306		1,463	5,769
Transfer from other comprehensive income into earnings				17		5	22
Net derivative instrument gain, net of tax				246		96	342
Balance, ending at Mar. 31, 2017	31	63,879	410,957	(53,413)	(37,475)	119,746	503,725
Balance, beginning at Dec. 31, 2017	31	66,004	422,570	(17,832)	(37,475)	137,339	570,637
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options		1,003					1,003
Net income			15,909			5,953	21,862
Dividends			(6,569)			(362)	(6,931)
Share based compensation		281	155			127	563
Foreign currency translation adjustment, net of tax				9,473		3,770	13,243
Transfer from other comprehensive income into earnings				(30)		(8)	(38)
Net derivative instrument gain, net of tax				(37)		(26)	(63)
Balance, ending at Mar. 31, 2018	$ 31	$ 67,288	$ 432,065	$ (8,426)	$ (37,475)	$ 146,793	$ 600,276