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, 2020	$ 36,259	$ 961,404	$ 1,723,777	$ (1,822,579)	$ 2,339	$ 901,200
Net income			121,922			121,922
Dividends paid			(10,864)			(10,864)
Stock awards and exercise of stock options	126	37,637		(13,255)		24,508
Purchases of treasury stock				(166,649)		(166,649)
Other		656		157	(156)	657
Balance at Jun. 30, 2021	36,385	999,697	1,834,835	(2,002,326)	2,183	870,774
Balance at Mar. 31, 2021	36,345	982,739	1,783,740	(1,876,315)	2,375	928,884
Net income			56,522			56,522
Dividends paid			(5,427)			(5,427)
Stock awards and exercise of stock options	40	16,630		(4,323)		12,347
Purchases of treasury stock				(121,882)		(121,882)
Other		328		194	(192)	330
Balance at Jun. 30, 2021	36,385	999,697	1,834,835	(2,002,326)	2,183	870,774
Balance at Dec. 31, 2021	36,514	1,044,341	1,970,311	(2,430,094)	2,201	623,273
Net income			130,625			130,625
Dividends paid			(10,722)			(10,722)
Stock awards and exercise of stock options	137	44,877		(25,926)		19,088
Purchases of treasury stock				(77,214)		(77,214)
Other		(89)		(72)	71	(90)
Balance at Jun. 30, 2022	36,651	1,089,129	2,090,214	(2,533,306)	2,272	684,960
Balance at Mar. 31, 2022	36,579	1,064,448	2,029,158	(2,465,716)	2,236	666,705
Net income			66,456			66,456
Dividends paid			(5,400)			(5,400)
Stock awards and exercise of stock options	72	25,274		(17,693)		7,653
Purchases of treasury stock				(49,861)		(49,861)
Other		(593)		(36)	36	(593)
Balance at Jun. 30, 2022	$ 36,651	$ 1,089,129	$ 2,090,214	$ (2,533,306)	$ 2,272	$ 684,960