Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Capital In Excess of Par Value	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock	Stockholders' Equity	Stockholders' Equity Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2018			125,871,866
Beginning balance at Dec. 31, 2018	$ 235,701		$ 1,259	$ 115,725	$ 1,166,762		$ (10,289)		$ (1,037,795)	$ 235,662		$ 39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	49,110				48,978					48,978		132
Dividends declared	(16,323)				(16,323)					(16,323)
Currency translation adjustments	943						943			943
Derivative financial instruments	(582)						(582)			(582)
Defined benefit obligations	511						511			511
Available-for-sale investments	24						24			24
Exercises of stock options (in shares)			58,655
Exercises of stock options	1,276		$ 1	1,275						1,276
Shares placed in treasury	(29,027)								(29,027)	(29,027)
Stock-based compensation charges (in shares)			449,275
Stock-based compensation charges	2,529		$ 4	2,525						2,529
Distributions to noncontrolling interests	(146)											(146)
Ending balance (in shares) at Mar. 31, 2019			126,379,796
Ending balance at Mar. 31, 2019	242,874		$ 1,264	119,525	1,198,198		(9,316)		(1,066,822)	242,849		25
Beginning balance (in shares) at Dec. 31, 2018			125,871,866
Beginning balance at Dec. 31, 2018	235,701		$ 1,259	115,725	1,166,762		(10,289)		(1,037,795)	235,662		39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	108,110
Currency translation adjustments	5,238
Ending balance (in shares) at Jun. 30, 2019			126,416,746
Ending balance at Jun. 30, 2019	294,149		$ 1,264	124,105	1,240,775		(4,932)		(1,067,082)	294,130		19
Beginning balance (in shares) at Mar. 31, 2019			126,379,796
Beginning balance at Mar. 31, 2019	242,874		$ 1,264	119,525	1,198,198		(9,316)		(1,066,822)	242,849		25
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	59,000				58,878					58,878		122
Dividends declared	(16,301)				(16,301)					(16,301)
Currency translation adjustments	4,295						4,295			4,295
Derivative financial instruments	(431)						(431)			(431)
Defined benefit obligations	493						493			493
Available-for-sale investments	27						27			27
Exercises of stock options (in shares)			32,023
Exercises of stock options	757			757						757
Shares placed in treasury	(260)								(260)	(260)
Stock-based compensation charges (in shares)			4,927
Stock-based compensation charges	3,823			3,823						3,823
Distributions to noncontrolling interests	(128)											(128)
Ending balance (in shares) at Jun. 30, 2019			126,416,746
Ending balance at Jun. 30, 2019	$ 294,149		$ 1,264	124,105	1,240,775		(4,932)		(1,067,082)	294,130		19
Beginning balance (in shares) at Dec. 31, 2019	126,579,285		126,579,285
Beginning balance at Dec. 31, 2019	$ 404,112	$ (1,142)	$ 1,266	134,069	1,344,383	$ (1,219)	(7,448)	$ 77	(1,068,164)	404,106	$ (1,142)	6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	75,620				75,499					75,499		121
Dividends declared	(18,254)				(18,254)					(18,254)
Currency translation adjustments	(11,940)						(11,940)			(11,940)
Derivative financial instruments	733						733			733
Defined benefit obligations	610						610			610
Available-for-sale investments	(600)						(600)			(600)
Exercises of stock options (in shares)			56,431
Exercises of stock options	1,332		$ 1	1,331						1,332
Shares placed in treasury	(25,076)								(25,076)	(25,076)
Stock-based compensation charges (in shares)			252,943
Stock-based compensation charges	3,102		$ 2	3,100						3,102
Distributions to noncontrolling interests	(127)											(127)
Ending balance (in shares) at Mar. 31, 2020			126,888,659
Ending balance at Mar. 31, 2020	$ 429,512		$ 1,269	138,500	1,401,628		(18,645)		(1,093,240)	429,512		0
Beginning balance (in shares) at Dec. 31, 2019	126,579,285		126,579,285
Beginning balance at Dec. 31, 2019	$ 404,112	$ (1,142)	$ 1,266	134,069	1,344,383	$ (1,219)	(7,448)	$ 77	(1,068,164)	404,106	$ (1,142)	6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	140,016
Currency translation adjustments	$ (11,084)
Ending balance (in shares) at Jun. 30, 2020	126,949,882		126,949,882
Ending balance at Jun. 30, 2020	$ 481,532		$ 1,269	143,412	1,447,642		(17,519)		(1,093,287)	481,517		15
Beginning balance (in shares) at Mar. 31, 2020			126,888,659
Beginning balance at Mar. 31, 2020	429,512		$ 1,269	138,500	1,401,628		(18,645)		(1,093,240)	429,512		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	64,396				64,258					64,258		138
Dividends declared	(18,244)				(18,244)					(18,244)
Currency translation adjustments	856						856			856
Derivative financial instruments	(493)						(493)			(493)
Defined benefit obligations	609						609			609
Available-for-sale investments	154						154			154
Exercises of stock options (in shares)			22,556
Exercises of stock options	537			537						537
Shares placed in treasury	(47)								(47)	(47)
Stock-based compensation charges (in shares)			38,667
Stock-based compensation charges	4,375			4,375						4,375
Distributions to noncontrolling interests	$ (123)											(123)
Ending balance (in shares) at Jun. 30, 2020	126,949,882		126,949,882
Ending balance at Jun. 30, 2020	$ 481,532		$ 1,269	$ 143,412	$ 1,447,642		$ (17,519)		$ (1,093,287)	$ 481,517		$ 15