Condensed Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2018		$ 12,185	$ 138,210	$ 2,530,088
Share repurchases		(211)		(205,135)
Cash dividends declared				(41,018)
Share-based compensation and restricted share issuances, net of forfeitures		10	5,353
Taxes paid in exchange for shares withheld		(2)	(1,446)
Net income				471,494
Balance at Sep. 30, 2019	$ 2,909,528	11,982	142,117	2,755,429
Balance at Jun. 30, 2019		12,020	140,970	2,645,495
Share repurchases		(38)		(40,576)
Cash dividends declared				(13,589)
Share-based compensation and restricted share issuances, net of forfeitures			1,147
Net income				164,099
Balance at Sep. 30, 2019	2,909,528	11,982	142,117	2,755,429
Balance at Dec. 31, 2019	3,080,717	11,953	218,462	2,850,302
Share repurchases		(223)		(306,568)
Cash dividends declared				(53,475)
Share-based compensation and restricted share issuances, net of forfeitures		6	8,371
Taxes paid in exchange for shares withheld		(2)	(2,731)
Forward contract for accelerated share repurchases			(37,500)
Cash paid for fractional shares		(1)	(611)
Net income				482,850
Balance at Sep. 30, 2020	3,170,833	11,733	185,991	2,973,109
Balance at Jun. 30, 2020		11,734	181,895	2,788,839
Cash dividends declared				(17,598)
Share-based compensation and restricted share issuances, net of forfeitures		(1)	4,096
Net income				201,868
Balance at Sep. 30, 2020	$ 3,170,833	$ 11,733	$ 185,991	$ 2,973,109