Income Taxes (Schedule Of Effective Income Tax Rates Different From Statutory Federal Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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%	0.40%	0.30%
Domestic production exclusion	(2.70%)	(2.80%)	(2.60%)
Research tax credit	(0.80%)	(0.80%)	(2.00%)
Reduction in Reserve for Uncertain Tax Provisions	(0.20%)	(0.60%)	(0.00%)
Other	0.10%	0.10%	(0.20%)
Effective income tax rate	31.90%	31.30%	30.50%
Reductions related to prior tax year amended tax filings			1.30%