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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share[Abstract]
Earnings	$ 67,722	$ 58,947	$ 205,714	$ 154,343
Diluted earnings	$ 67,722	$ 58,947	$ 205,714	$ 154,343
Earnings, Shares	15,940	15,970	15,948	15,952
Dilutive stock options, Shares	358	500	394	484
Nonvested stock awards, Shares	75	85	77	78
Diluted earnings, Shares	16,373	16,555	16,419	16,514
Earnings, Earnings per Share	$ 4.25	$ 3.69	$ 12.90	$ 9.68
Diluted earnings, Earnings per Share	$ 4.14	$ 3.56	$ 12.53	$ 9.35