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	51,820					(15)	51,805
Foreign currency translation adjustments		23,184				2	23,186
Changes in unrecognized pension gains/losses and related amortization, net of tax		879					879
Changes in treasury locks, net of tax		7					7
Stock awards and option exercises			4	7,538	18,912		26,454
Cash dividends declared on common stock	(19,937)						(19,937)
Common stock repurchased and retired	(14,080)		(2)		(1,937)		(16,019)
Balance at Mar. 31, 2017	1,215,037	(295,639)	662	(243,379)	563,657	279	1,240,617
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	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