Consolidated Statements Of Changes In Stockholders' Equity - USD ($) $ in Thousands	Capital Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock-At Cost [Member]	Deferred Compensation Payable In Company Stock [Member]	Total
Balance at Dec. 31, 2016	$ 34,270	$ 639,703	$ 958,149	$ (1,110,536)	$ 2,513	$ 524,099
Net income			98,177			98,177
Dividends paid			(17,371)			(17,371)
Stock awards and exercise of stock options (Note 4)	462	55,264		(26,467)		29,259
Purchases of treasury stock (Note 18)				(94,640)		(94,640)
Other		830		311	(311)	830
Balance at Dec. 31, 2017	34,732	695,797	1,038,955	(1,231,332)	2,202	540,354
Net income			205,544			205,544
Dividends paid			(18,662)			(18,662)
Stock awards and exercise of stock options (Note 4)	579	79,452		(55,939)		24,092
Purchases of treasury stock (Note 18)				(158,884)		(158,884)
Other		(891)	(220)	(141)	142	(1,110)
Balance at Dec. 31, 2018	35,311	774,358	1,225,617	(1,446,296)	2,344	591,334
Net income			219,923			219,923
Dividends paid			(19,788)			(19,788)
Stock awards and exercise of stock options (Note 4)	500	85,788		(59,043)		27,245
Purchases of treasury stock (Note 18)				(92,631)		(92,631)
Other		525		30	(30)	525
Balance at Dec. 31, 2019	$ 35,811	$ 860,671	$ 1,425,752	$ (1,597,940)	$ 2,314	$ 726,608