CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Noncontrolling Interests
Common Stock, Dividends, Per Share, Declared	$ 0.39
Beginning balance at Dec. 31, 2017	$ 932,453	$ 9,858	$ 334,309	$ 2,388,219	$ (247,186)	$ (1,553,563)	$ 816
Beginning Balance (in shares) at Dec. 31, 2017		65,663,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	60,820			60,824			(4)
Unrecognized amounts from defined benefit pension plans, net of tax	1,287				1,287
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	855				855
Currency translation adjustment	19,387				19,328		59
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(25,787)			(25,787)
Stock-based compensation activity		55,000
Issuance of shares under benefit plans	6,381		5,819			562
Purchase of treasury shares	(14,724)					(14,724)
Purchase of shares for treasury (in shares)		(159,000)
Stockholders' Equity, Other	0		5,483	(5,483)
Ending balance at Mar. 31, 2018	$ 980,672	$ 9,858	345,611	2,417,773	(225,716)	(1,567,725)	871
Ending Balance (in shares) at Mar. 31, 2018		65,559,000
Common Stock, Dividends, Per Share, Declared	$ 1.17
Beginning balance at Dec. 31, 2017	$ 932,453	$ 9,858	334,309	2,388,219	(247,186)	(1,553,563)	816
Beginning Balance (in shares) at Dec. 31, 2017		65,663,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	200,214
Unrecognized amounts from defined benefit pension plans, net of tax	5,863
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	1,039
Currency translation adjustment	(31,422)
Ending balance at Sep. 30, 2018	$ 927,868	$ 9,858	357,749	2,505,396	(271,614)	(1,674,232)	711
Ending Balance (in shares) at Sep. 30, 2018		64,446,000
Common Stock, Dividends, Per Share, Declared	$ 0.39
Beginning balance at Mar. 31, 2018	$ 980,672	$ 9,858	345,611	2,417,773	(225,716)	(1,567,725)	871
Beginning Balance (in shares) at Mar. 31, 2018		65,559,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	68,859			68,864			(5)
Unrecognized amounts from defined benefit pension plans, net of tax	721				721
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	(1,232)				(1,232)
Currency translation adjustment	(50,342)				(50,252)		(90)
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(25,701)			(25,701)
Stock-based compensation activity		15,000
Issuance of shares under benefit plans	6,039		6,215			(176)
Purchase of treasury shares	(35,508)					(35,508)
Purchase of shares for treasury (in shares)		(402,000)
Stockholders' Equity, Other	0		(194)	194
Ending balance at Jun. 30, 2018	$ 943,508	$ 9,858	351,632	2,461,130	(276,479)	(1,603,409)	776
Ending Balance (in shares) at Jun. 30, 2018		65,172,000
Common Stock, Dividends, Per Share, Declared	$ 0.39
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	$ 70,535			70,539			(4)
Unrecognized amounts from defined benefit pension plans, net of tax	3,855				3,855
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	1,416				1,416
Currency translation adjustment	(467)				(406)		(61)
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(25,346)			(25,346)
Stock-based compensation activity		41,000
Issuance of shares under benefit plans	5,612		5,190			422
Purchase of treasury shares	(71,245)					(71,245)
Purchase of shares for treasury (in shares)		(767,000)
Stockholders' Equity, Other	0		927	(927)
Ending balance at Sep. 30, 2018	$ 927,868	$ 9,858	357,749	2,505,396	(271,614)	(1,674,232)	711
Ending Balance (in shares) at Sep. 30, 2018		64,446,000
Common Stock, Dividends, Per Share, Declared	$ 0.47
Beginning balance at Dec. 31, 2018	$ 887,592	$ 9,858	360,308	2,564,440	(293,739)	(1,753,925)	650
Beginning Balance (in shares) at Dec. 31, 2018		63,546,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	71,466			71,480			(14)
Unrecognized amounts from defined benefit pension plans, net of tax	787				787
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	329				329
Currency translation adjustment	5,136				5,099		37
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(29,847)			(29,847)
Stock-based compensation activity		148,000
Issuance of shares under benefit plans	4,786		3,302			1,484
Purchase of treasury shares	(75,584)					(75,584)
Purchase of shares for treasury (in shares)		(894,000)
Stockholders' Equity, Other	0		808	(808)
Ending balance at Mar. 31, 2019	$ 864,665	$ 9,858	364,418	2,605,265	(287,524)	(1,828,025)	673
Ending Balance (in shares) at Mar. 31, 2019		62,800,000
Common Stock, Dividends, Per Share, Declared	$ 1.41
Beginning balance at Dec. 31, 2018	$ 887,592	$ 9,858	360,308	2,564,440	(293,739)	(1,753,925)	650
Beginning Balance (in shares) at Dec. 31, 2018		63,546,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	229,367
Unrecognized amounts from defined benefit pension plans, net of tax	2,491
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	(320)
Currency translation adjustment	$ (14,040)
Purchase of shares for treasury (in shares)	(2,600,000)
Ending balance at Sep. 30, 2019	$ 813,808	$ 9,858	377,584	2,704,486	(305,868)	(1,973,136)	884
Ending Balance (in shares) at Sep. 30, 2019		61,149,000
Common Stock, Dividends, Per Share, Declared	$ 0.47
Beginning balance at Mar. 31, 2019	$ 864,665	$ 9,858	364,418	2,605,265	(287,524)	(1,828,025)	673
Beginning Balance (in shares) at Mar. 31, 2019		62,800,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	85,444			85,452			(8)
Unrecognized amounts from defined benefit pension plans, net of tax	1,091				1,091
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	(301)				(301)
Currency translation adjustment	4,849				4,884		(35)
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(29,279)			(29,279)
Stock-based compensation activity		13,000
Issuance of shares under benefit plans	4,919		4,783			136
Purchase of treasury shares	(85,330)					(85,330)
Purchase of shares for treasury (in shares)		(1,034,000)
Stockholders' Equity, Other	0		(282)	282
Ending balance at Jun. 30, 2019	$ 846,058	$ 9,858	368,919	2,661,720	(281,850)	(1,913,219)	630
Ending Balance (in shares) at Jun. 30, 2019		61,779,000
Common Stock, Dividends, Per Share, Declared	$ 0.47
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income including non-controlling interests	$ 72,457			72,461			(4)
Unrecognized amounts from defined benefit pension plans, net of tax	613				613
Unrealized gain (loss) on derivatives designated and qualifying as cash flow hedges, net of tax	(348)				(348)
Currency translation adjustment	(24,025)				(24,283)		258
Cash dividends declared - $0.47 per share and $0.39 per share in 2019 and 2018, respectively	(28,931)			(28,931)
Stock-based compensation activity		107,000
Issuance of shares under benefit plans	9,107		7,996			1,111
Purchase of treasury shares	$ (61,028)					(61,028)
Purchase of shares for treasury (in shares)	(700,000)	(737,000)
Stockholders' Equity, Other	$ (95)		669	(764)
Ending balance at Sep. 30, 2019	$ 813,808	$ 9,858	$ 377,584	$ 2,704,486	$ (305,868)	$ (1,973,136)	$ 884
Ending Balance (in shares) at Sep. 30, 2019		61,149,000