Income Taxes (Schedule Of Difference Between Actual Income Tax Provision For Continuing Operations And Income Tax Provision Calculated At Statutory U.S. Federal Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Income tax provision calculated using the statutory rate of 21%	$ 83,158	$ 54,938	$ 50,316
Excess stock compensation tax benefits	(26,089)	(24,177)	(22,862)
State and local income taxes, less federal income tax effect	13,855	7,880	7,150
Nondeductible expenses	5,377	3,048	2,280
Other --net	223	(3)	(2,828)
Income tax provision	$ 76,524	$ 41,686	$ 34,056
Effective tax rate	19.30%	15.90%	14.20%