Consolidated Condensed Statements of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	AOCI Attributable to Parent	Retained Earnings
Beginning Balance at Dec. 31, 2017	$ 553,874	$ 265,048	$ 15,625	$ (20,444)	$ 293,645
Beginning Balance (in shares) at Dec. 31, 2017		36,761,000
Cumulative effect of accounting change due to adoption of ASU | ASU 2014-09	(3,264)				(3,264)
Cumulative effect of accounting change due to adoption of ASU | ASU 2016-16	31,645				31,645
Cumulative effect of accounting change due to adoption of ASU | ASU 2018-02				(40)	40
Exercise of Common Stock options for cash	751	$ 1,061	(310)
Exercise of Common Stock options for cash (in shares)		57,000
Cancellation of restricted stock	(659)	$ (659)
Cancelation of restricted stock (in shares)		(24,000)
Stock option compensation	840		840
Common Stock issued to Board of Directors and employees	1,362	$ 1,362
Currency translation, net	11,665			11,665
Foreign currency hedge, net	1,545			1,545
Commodity hedge, net	(277)			(277)
Net income	12,966				12,966
Ending Balance at Mar. 31, 2018	610,448	$ 266,812	16,155	(7,551)	335,032
Ending Balance (in shares) at Mar. 31, 2018		36,794,000
Beginning Balance at Dec. 31, 2017	553,874	$ 265,048	15,625	(20,444)	293,645
Beginning Balance (in shares) at Dec. 31, 2017		36,761,000
Net income	29,270
Ending Balance at Sep. 30, 2018	550,321	$ 218,569	14,293	(33,877)	351,336
Ending Balance (in shares) at Sep. 30, 2018		35,749,000
Beginning Balance at Mar. 31, 2018	610,448	$ 266,812	16,155	(7,551)	335,032
Beginning Balance (in shares) at Mar. 31, 2018		36,794,000
Stock repurchase	(20,241)	$ (20,241)
Stock repurchase (in shares)		(629,000)
Exercise of Common Stock options for cash	4,215	$ 5,335	(1,120)
Exercise of Common Stock options for cash (in shares)		241,000
Cancellation of restricted stock	(223)	$ (223)
Cancelation of restricted stock (in shares)		(25,000)
Stock option compensation	803		803
Common Stock issued to Board of Directors and employees	1,057	$ 1,057
Commons stock issued to Board of Directors and employees (in shares)		20,000
Currency translation, net	(23,150)			(23,150)
Foreign currency hedge, net	(1,142)			(1,142)
Net income	16,659				16,659
Ending Balance at Jun. 30, 2018	588,426	$ 252,740	15,838	(31,843)	351,691
Ending Balance (in shares) at Jun. 30, 2018		36,401,000
Stock repurchase	(47,111)	$ (47,111)
Stock repurchase (in shares)		(938,000)
Exercise of Common Stock options for cash	9,098	$ 11,466	(2,368)
Exercise of Common Stock options for cash (in shares)		284,000
Stock option compensation	823		823
Common Stock issued to Board of Directors and employees	1,474	$ 1,474
Commons stock issued to Board of Directors and employees (in shares)		2,000
Currency translation, net	(3,251)			(3,251)
Foreign currency hedge, net	1,217			1,217
Net income	(355)				(355)
Ending Balance at Sep. 30, 2018	550,321	$ 218,569	14,293	(33,877)	351,336
Ending Balance (in shares) at Sep. 30, 2018		35,749,000
Beginning Balance at Dec. 31, 2018	$ 479,699	$ 140,300	14,934	(39,500)	363,965
Beginning Balance (in shares) at Dec. 31, 2018	33,856,629	33,857,000
Cumulative effect of accounting change due to adoption of ASU | ASU 2016-02	$ 261				261
Stock repurchase	(8,040)	$ (8,040)
Stock repurchase (in shares)		(200,000)
Exercise of Common Stock options for cash	214	$ 1,021	(807)
Exercise of Common Stock options for cash (in shares)		13,000
Cancellation of restricted stock	(376)	$ (376)
Cancelation of restricted stock (in shares)		(17,000)
Stock option compensation	386		386
Common Stock issued to Board of Directors and employees	1,581	$ 1,581
Currency translation, net	(4,251)			(4,251)
Foreign currency hedge, net	599			599
Net income	8,414				8,414
Ending Balance at Mar. 31, 2019	478,487	$ 134,486	14,513	(43,152)	372,640
Ending Balance (in shares) at Mar. 31, 2019		33,653,000
Beginning Balance at Dec. 31, 2018	$ 479,699	$ 140,300	14,934	(39,500)	363,965
Beginning Balance (in shares) at Dec. 31, 2018	33,856,629	33,857,000
Net income	$ 27,052
Ending Balance at Sep. 30, 2019	$ 451,593	$ 103,781	11,348	(54,814)	391,278
Ending Balance (in shares) at Sep. 30, 2019	32,741,826	32,742,000
Beginning Balance at Mar. 31, 2019	$ 478,487	$ 134,486	14,513	(43,152)	372,640
Beginning Balance (in shares) at Mar. 31, 2019		33,653,000
Stock repurchase	(25,000)	$ (25,000)
Stock repurchase (in shares)		(630,000)
Exercise of Common Stock options for cash	4,557	$ 4,936	(379)
Exercise of Common Stock options for cash (in shares)		116,000
Cancellation of restricted stock	(550)	$ (550)
Cancelation of restricted stock (in shares)		(21,000)
Stock option compensation	(114)		(114)
Common Stock issued to Board of Directors and employees	1,438	$ 1,438
Commons stock issued to Board of Directors and employees (in shares)		30,000
Currency translation, net	3,480			3,480
Foreign currency hedge, net	232			232
Net income	2,751				2,751
Ending Balance at Jun. 30, 2019	465,281	$ 115,310	14,020	(39,440)	375,391
Ending Balance (in shares) at Jun. 30, 2019		33,148,000
Stock repurchase	(25,000)	$ (25,000)
Stock repurchase (in shares)		(635,000)
Exercise of Common Stock options for cash	9,108	$ 12,201	(3,093)
Exercise of Common Stock options for cash (in shares)		228,000
Cancellation of restricted stock	(287)	$ (287)
Cancelation of restricted stock (in shares)		(12,000)
Stock option compensation	421		421
Common Stock issued to Board of Directors and employees	1,557	$ 1,557
Commons stock issued to Board of Directors and employees (in shares)		13,000
Currency translation, net	(15,172)			(15,172)
Foreign currency hedge, net	(202)			(202)
Net income	15,887				15,887
Ending Balance at Sep. 30, 2019	$ 451,593	$ 103,781	$ 11,348	$ (54,814)	$ 391,278
Ending Balance (in shares) at Sep. 30, 2019	32,741,826	32,742,000