CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - 9 months ended Sep. 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	[1]
Balance (in shares) at Dec. 31, 2017	216,544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	$ 39	$ 7,165			7,204
Stock issued for stock incentive plans, net (in shares)	391
Stock purchased and retired	$ (213)	$ (7,165)	(32,782)		(40,160)
Stock purchased and retired (in shares)	(2,137)
Net income			162,040		162,040
Dividends			(64,636)		(64,636)
Pension adjustment, net of taxes				485	485
Foreign currency translation				(29)	(29)
Balance at Sep. 30, 2018	$ 21,480		971,382	(16,261)	$ 976,601
Balance (in shares) at Sep. 30, 2018	214,798
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standard (Note 2)			$ 15	$ (15)

[1] (Note 1)