Income Taxes (Schedule Of Effective Income Tax Rates Different From Statutory Federal Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit	0.50%	0.50%	0.40%
Domestic production exclusion	(2.80%)	(2.70%)	(2.80%)
Research tax credit	(0.80%)	(0.80%)	(0.80%)
Increase (Reduction) in Reserve for Uncertain Tax Provisions	0.10%	(0.20%)	(0.60%)
Change in Tax Rate on Deferred Taxes	(7.20%)	0.00%	0.00%
Foreign Tax Credit	(0.80%)	(0.00%)	(0.00%)
Other	(0.50%)	0.10%	0.10%
Effective income tax rate	23.50%	31.90%	31.30%