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, 2018	$ 1,371,826	$ (310,504)	$ 673	$ (318,208)	$ 678,769	$ 315	$ 1,422,871
Increase (Decrease) in Stockholders' Equity
Net Income	136,919					1	136,920
Foreign currency translation adjustments		(197)					(197)
Changes in unrecognized pension gains (losses) and related amortization, net of tax		1,437					1,437
Changes in derivative gains (losses), net of tax		(872)					(872)
Stock awards and option exercises			10	19,924	64,563		84,497
Cash dividends declared on common stock	(44,138)						(44,138)
Treasury stock purchased				(19,096)			(19,096)
Balance at Jun. 30, 2019	1,464,607	(310,136)	683	(317,380)	743,332	316	1,581,422
Balance at Mar. 31, 2019	1,413,453	(319,795)	676	(327,871)	700,933	318	1,467,714
Increase (Decrease) in Stockholders' Equity
Net Income	73,915					6	73,921
Foreign currency translation adjustments		9,422				(8)	9,414
Changes in unrecognized pension gains (losses) and related amortization, net of tax		716					716
Changes in derivative gains (losses), net of tax		(479)					(479)
Stock awards and option exercises			7	14,587	42,399		56,993
Cash dividends declared on common stock	(22,761)						(22,761)
Treasury stock purchased				(4,096)			(4,096)
Balance at Jun. 30, 2019	1,464,607	(310,136)	683	(317,380)	743,332	316	1,581,422
Balance at Dec. 31, 2019	1,523,820	(341,948)	686	(381,238)	770,596	336	1,572,252
Increase (Decrease) in Stockholders' Equity
Net Income	97,092					18	97,110
Adoption of accounting standards | Accounting Standards Update 2016-13	(1,377)						(1,377)
Foreign currency translation adjustments		(23,134)				1	(23,133)
Changes in unrecognized pension gains (losses) and related amortization, net of tax		3,076					3,076
Changes in derivative gains (losses), net of tax		750					750
Stock awards and option exercises			4	10,532	32,915		43,451
Cash dividends declared on common stock	(46,143)						(46,143)
Balance at Jun. 30, 2020	1,573,392	(361,256)	690	(370,706)	803,511	355	1,645,986
Balance at Mar. 31, 2020	1,554,665	(381,058)	689	(372,573)	785,567	333	1,587,623
Increase (Decrease) in Stockholders' Equity
Net Income	41,839					21	41,860
Foreign currency translation adjustments		19,095				1	19,096
Changes in unrecognized pension gains (losses) and related amortization, net of tax		1,440					1,440
Changes in derivative gains (losses), net of tax		(733)					(733)
Stock awards and option exercises			1	1,867	17,944		19,812
Cash dividends declared on common stock	(23,112)						(23,112)
Balance at Jun. 30, 2020	$ 1,573,392	$ (361,256)	$ 690	$ (370,706)	$ 803,511	$ 355	$ 1,645,986