Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings	$ 72,003	$ 67,722	$ 193,925	$ 205,714
Diluted earnings	$ 72,003	$ 67,722	$ 193,925	$ 205,714
Earnings, Shares	15,587	15,940	15,808	15,948
Dilutive stock options, Shares	215	358	233	394
Nonvested stock awards, Shares	40	75	42	77
Diluted earnings, Shares	15,842	16,373	16,083	16,419
Earnings, Earnings per Share	$ 4.62	$ 4.25	$ 12.27	$ 12.90
Diluted earnings, Earnings per Share	$ 4.55	$ 4.14	$ 12.06	$ 12.53