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, 2017	$ 1,301,147	$ (253,302)	$ 667	$ (346,245)	$ 609,471	$ 310	$ 1,312,048
Increase (Decrease) in Stockholders' Equity
Net Income	59,300					(12)	59,288
Adoption of accounting standards | Accounting Standards Update 2014-09	2,937						2,937
Foreign currency translation adjustments		22,924				11	22,935
Changes in unrecognized pension gains (losses) and related amortization, net of tax		1,356					1,356
Changes in treasury locks, net of tax		7					7
Changes in derivative gains (losses), net of tax		346					346
Stock awards and option exercises			5	12,174	30,212		42,391
Cash dividends declared on common stock	(19,830)						(19,830)
Treasury stock purchased				(3,905)			(3,905)
Common stock repurchased and retired	(11,336)		(1)		(1,460)		(12,797)
Balance at Mar. 31, 2018	1,332,218	(228,669)	671	(337,976)	638,223	309	1,404,776
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	63,004					(5)	62,999
Foreign currency translation adjustments		(9,619)				8	(9,611)
Changes in unrecognized pension gains (losses) and related amortization, net of tax		721					721
Changes in derivative gains (losses), net of tax		(393)					(393)
Stock awards and option exercises			3	5,337	22,164		27,504
Cash dividends declared on common stock	(21,377)						(21,377)
Treasury stock purchased				(15,000)			(15,000)
Balance at Mar. 31, 2019	$ 1,413,453	$ (319,795)	$ 676	$ (327,871)	$ 700,933	$ 318	$ 1,467,714