Earnings Per Share (Schedule Of Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share[Abstract]
Earnings	$ 319,466	$ 219,923	$ 205,544
Diluted earnings	$ 319,466	$ 219,923	$ 205,544
Earnings, Shares	15,955	15,969	16,059
Dilutive stock options, Shares	368	480	650
Nonvested stock awards, Shares	75	78	94
Diluted earnings, Shares	16,398	16,527	16,803
Earnings, Earnings per Share	$ 20.02	$ 13.77	$ 12.80
Diluted earnings, Earnings per Share	$ 19.48	$ 13.31	$ 12.23