Income Taxes (Schedule Of Effective Tax Rate) (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Taxes [Abstract]
Statutory U.S. federal income tax rate	21.00%	35.00%	21.00%	35.00%	35.00%
State income tax, net of related federal income tax benefit	6.20%	4.50%	6.20%	4.50%
Foreign operations	0.90%	1.00%	0.90%	1.00%
Federal credits	(1.70%)	(0.90%)	(1.70%)	(0.90%)
Executive compensation disallowed	2.10%	0.10%	2.10%	0.10%
Meals and entertainment	1.60%	0.00%	1.60%	0.00%
Other	(1.60%)	(0.90%)	0.40%	(1.20%)
Equity compensation related adjustments	8.30%	0.20%	5.30%	(0.30%)
Effective income tax rate	36.80%	39.00%	35.80%	38.20%