CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)	Common Stock Par Value	Treasury Stock	Capital in Excess of Par Value	Non-Controlling Interest	Total
Balance at Dec. 31, 2016	$ 1,197,234	$ (319,709)	$ 660	$ (250,917)	$ 546,682	$ 292	$ 1,174,242
Increase (Decrease) in Stockholders' Equity
Net Income	170,517					6	170,523
Foreign currency translation adjustments		69,493				12	69,505
Changes in unrecognized pension gains/losses and related amortization, net of tax		2,699					2,699
Changes in treasury locks, net of tax		21					21
Changes in derivative gains/losses, net of tax		(3,591)					(3,591)
Stock awards and option exercises			11	23,938	57,742		81,691
Cash dividends declared on common stock	(60,002)						(60,002)
Treasury stock purchased				(72,270)			(72,270)
Common stock repurchased and retired	(36,173)		(5)		(4,816)		(40,994)
Balance at Sep. 30, 2017	1,271,576	(251,087)	666	(299,249)	599,608	310	1,321,824
Balance at Jun. 30, 2017	1,238,123	(266,325)	665	(257,731)	594,145	299	1,309,176
Increase (Decrease) in Stockholders' Equity
Net Income	53,523					6	53,529
Foreign currency translation adjustments		17,898				5	17,903
Changes in unrecognized pension gains/losses and related amortization, net of tax		924					924
Changes in treasury locks, net of tax		7					7
Changes in derivative gains/losses, net of tax		(3,591)					(3,591)
Stock awards and option exercises			1	4,024	5,463		9,488
Cash dividends declared on common stock	(20,070)						(20,070)
Treasury stock purchased				(45,542)			(45,542)
Balance at Sep. 30, 2017	1,271,576	(251,087)	666	(299,249)	599,608	310	1,321,824
Balance at Dec. 31, 2017	1,301,147	(253,302)	667	(346,245)	609,471	310	1,312,048
Increase (Decrease) in Stockholders' Equity
Net Income	154,071					20	154,091
Adoption of accounting standards	2,937						2,937
Foreign currency translation adjustments		(53,141)				(16)	(53,157)
Changes in unrecognized pension gains/losses and related amortization, net of tax		4,032					4,032
Changes in treasury locks, net of tax		17					17
Changes in derivative gains/losses, net of tax		1,046					1,046
Stock awards and option exercises			11	26,009	67,705		93,725
Cash dividends declared on common stock	(60,989)						(60,989)
Treasury stock purchased				(3,905)			(3,905)
Common stock repurchased and retired	(51,315)		(6)		(6,466)		(57,787)
Balance at Sep. 30, 2018	1,345,851	(301,348)	672	(324,141)	670,710	314	1,392,058
Balance at Jun. 30, 2018	1,328,034	(291,660)	668	(336,278)	646,449	299	1,347,512
Increase (Decrease) in Stockholders' Equity
Net Income	38,996					26	39,022
Foreign currency translation adjustments		(9,858)				(11)	(9,869)
Changes in unrecognized pension gains/losses and related amortization, net of tax		1,333					1,333
Changes in treasury locks, net of tax		3					3
Changes in derivative gains/losses, net of tax		(1,166)					(1,166)
Stock awards and option exercises			4	12,137	24,261		36,402
Cash dividends declared on common stock	(21,179)						(21,179)
Balance at Sep. 30, 2018	$ 1,345,851	$ (301,348)	$ 672	$ (324,141)	$ 670,710	$ 314	$ 1,392,058