Income Taxes (Reconciliation From Statutory Federal Income Tax Rate To Effective Income Tax Rate) (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 tax on commercial operations, net of federal benefits	0.10%	0.70%	1.10%
Global impact of international operations	1.90%	0.20%	0.60%
Foreign derived intangible income	(2.10%)	(1.40%)	(1.20%)
Equity-based compensation	(0.20%)	(1.10%)	(1.10%)
Domestic tax credits	(4.60%)	(2.00%)	(1.10%)
Contract close-outs	0.00%	0.00%	(0.50%)
Other, net	(0.80%)	(0.30%)	(1.00%)
Effective income tax rate	15.30%	17.10%	17.80%