CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2012	$ 22,014		$ 891,464	$ (14,246)	$ 899,232
Balance (in shares) at Dec. 31, 2012	220,144,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	$ 70	$ 8,107			8,177
Stock issued for stock incentive plans, net (in shares)	699,000
Stock purchased and retired	$ (185)	(11,285)	(13,652)		(25,122)
Stock purchased and retired (in shares)	(1,857,000)
Net (loss) income			166,895		166,895
Pension adjustment, net of taxes				4,928	4,928
Foreign currency translation				(778)	(778)
Unrealized gain (loss) on securities, net of taxes and reclassification adjustment				(19)	(19)
Dividends declared			(87,789)		(87,789)
Excess tax benefits for share- based payments		3,178			3,178
Balance at Dec. 31, 2013	$ 21,899		956,918	(10,115)	968,702
Balance (in shares) at Dec. 31, 2013	218,986,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	$ 57	9,017			9,074
Stock issued for stock incentive plans, net (in shares)	569,000
Stock purchased and retired	$ (302)	(13,353)	(35,942)		(49,597)
Stock purchased and retired (in shares)	(3,016,000)
Net (loss) income			245,193		245,193
Pension adjustment, net of taxes				(6,486)	(6,486)
Foreign currency translation				(1,124)	(1,124)
Unrealized gain (loss) on securities, net of taxes and reclassification adjustment				(108)	(108)
Dividends declared			(91,608)		(91,608)
Excess tax benefits for share- based payments		4,336			4,336
Balance at Dec. 31, 2014	$ 21,654		1,074,561	(17,833)	$ 1,078,382
Balance (in shares) at Dec. 31, 2014	216,539,000				216,539,015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	$ 79	9,802			$ 9,881
Stock issued for stock incentive plans, net (in shares)	791,000
Stock purchased and retired	$ (34)	(11,212)	7,153		(4,093)
Stock purchased and retired (in shares)	(339,000)
Net (loss) income			(99,561)		(99,561)
Pension adjustment, net of taxes				1,531	1,531
Foreign currency translation				(1,801)	(1,801)
Unrealized gain (loss) on securities, net of taxes and reclassification adjustment				134	134
Dividends declared			(33,602)		(33,602)
Excess tax benefits for share- based payments		$ 1,410			1,410
Balance at Dec. 31, 2015	$ 21,699		$ 948,551	$ (17,969)	$ 952,281
Balance (in shares) at Dec. 31, 2015	216,991,000				216,991,357