CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ 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	$ 42	$ 4,544			4,586
Stock issued for stock incentive plans, net (in shares)	416
Stock purchased and retired	$ (213)	$ (4,544)	(35,339)		(40,096)
Stock purchased and retired (in shares)	(2,133)
Net income			112,073		112,073
Dividends			(43,186)		(43,186)
Pension adjustment, net of taxes				328	328
Foreign currency translation				(415)	(415)
Balance at Jun. 30, 2018	$ 21,483		940,308	(16,804)	$ 944,987
Balance (in shares) at Jun. 30, 2018	214,827
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standard (Note 2)			$ 15	$ (15)