Accounts Receivable (Schedule Of Accounts Receivable Under Long-Term Contracts) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Unbilled Receivables, Not Billable, Fiscal Year Maturity [Abstract]
Unbillable, current	$ 2,876	$ 1,919
Unbillable, expected to be collected after one year	1,564	2,011
Total Unbillable	4,440	3,930
Contracts Receivable, Claims and Uncertain Amounts, Fiscal Year Maturity [Abstract]
Claims, current	4	38
Claims, expected to be collected after one year	55	91
Total Claims	$ 59	$ 129