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 [Meber]	Noncontrolling Interest [Mmember]	Total
Balance, beginning at Dec. 31, 2015	$ 31	$ 62,030	$ 388,434	$ (48,091)	$ (36,817)	$ 110,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercise of stock options		1,235
Sale of subsidiary shares to noncontrolling interest		(154)				1,603
Net income			29,404			9,252	$ 38,656
Dividends			(13,980)			(4,863)
Share based compensation		630
Purchase of subsidiary shares from noncontrolling interest		(1,670)				(800)
Foreign currency translation adjustment, net of tax				7,363		3,141	10,504
Balance, ending at Sep. 30, 2016	31	62,071	403,858	(40,728)	(36,817)	119,133	507,548
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		839
Net income			37,194			12,287	49,481
Dividends			(15,899)			(5,947)
Share based compensation		703	536			391
Foreign currency translation adjustment, net of tax				34,882		13,833	48,715
Transfer from other comprehensive income into earnings				17		5
Net derivative instrument gain, net of tax				22		8
Balance, ending at Sep. 30, 2017	$ 31	$ 64,645	$ 424,545	$ (23,061)	$ (37,475)	$ 133,844	$ 562,529