Income Taxes (Schedule Of Effective Income Tax Rates Different From Statutory Federal Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	21.00%
State income taxes, net of federal income tax benefit	2.10%	0.60%	0.60%
Research tax credit	(1.40%)	(1.10%)	(0.80%)
(Decrease) Increase in reserve for uncertain tax provisions	(0.10%)	0.30%	0.10%
Change in tax rate on deferred taxes	0.00%	0.00%	0.50%
Foreign tax credit	(0.10%)	(0.10%)	(0.10%)
Foreign derived intangible income deduction	(5.20%)	(4.80%)	(4.60%)
Stock compensation	(1.00%)	(1.10%)	(1.00%)
Other	0.30%	0.30%	0.40%
Effective income tax rate	15.60%	15.10%	16.10%