CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss	Total
Balance at Dec. 31, 2017	$ 21,654		$ 906,745	$ (16,702)	$ 911,697
Balance (in shares) at Dec. 31, 2017	216,544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	$ 50	$ 2,505			2,555
Stock issued for stock incentive plans, net (in shares)	498
Stock purchased and retired	$ (157)	$ (2,505)	(28,048)		(30,710)
Stock purchased and retired (in shares)	(1,573)
Net income			52,130		52,130
Dividends			(21,657)		(21,657)
Pension adjustment, net of taxes				173	173
Foreign currency translation				(481)	(481)
Balance at Mar. 31, 2018	$ 21,547		909,185	(17,025)	$ 913,707
Balance (in shares) at Mar. 31, 2018	215,469
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standard (Note 2)			$ 15	$ (15)