Income Taxes (Tax Effects Of Temporary Differences Between Reported Earnings And Taxable Earnings) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Retirement benefits	$ 1,097	$ 1,055
Lease assets	418	0
Tax loss and credit carryforwards	323	393
Salaries and wages	167	160
Workers' compensation	148	138
Other	367	351
Deferred assets	2,520	2,097
Valuation allowance	(291)	(336)
Net deferred assets	2,229	1,761
Intangible assets	(1,070)	(1,061)
Lease liabilities	(418)	0
Contract accounting methods	(375)	(530)
Property, plant and equipment	(291)	(265)
Capital Construction Fund qualified ships	(164)	(160)
Other	(359)	(284)
Deferred liabilities	(2,677)	(2,300)
Net deferred tax liability	$ (448)	$ (539)