Income Taxes (Schedule of Deferred Income Tax) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Components of Deferred Tax Assets and Liabilities [Abstract]
Accrued employee compensation and benefits	$ 246	$ 209
Other accrued expenses and reserves	(21)	77
Contract balances and inventories	(611)	(494)
Pension benefits	1,701	1,306
Other retiree benefits	68	67
Operating lease right-of-use assets	(204)	(187)
Operating lease liabilities	214	196
Net operating loss and tax credit carryforwards	405	83
Depreciation and amortization	(921)	(827)
Partnership outside basis difference	(25)	(29)
Other	21	12
Valuation allowance	(360)	(84)
Deferred income taxes—noncurrent	$ 513	$ 329