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, 2018	$ 35,311	$ 774,358	$ 1,225,617	$ (1,446,296)	$ 2,344	$ 591,334
Net income			44,667			44,667
Dividends paid			(4,799)			(4,799)
Stock awards and exercise of stock options	210	29,152		(23,495)		5,867
Purchases of treasury stock				(49,250)		(49,250)
Other		191		(36)	36	191
Balance at Mar. 31, 2019	35,521	803,701	1,265,485	(1,519,077)	2,380	588,010
Balance at Dec. 31, 2019	35,811	860,671	1,425,752	(1,597,940)	2,314	726,608
Net income			55,891			55,891
Dividends paid			(5,130)			(5,130)
Stock awards and exercise of stock options	101	18,972		(11,140)		7,933
Purchases of treasury stock				(100,235)		(100,235)
Other		(1,093)	(362)	(75)	64	(1,466)
Balance at Mar. 31, 2020	$ 35,912	$ 878,550	$ 1,476,151	$ (1,709,390)	$ 2,378	$ 683,601