Income Taxes (Details 4) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets (Table Amounts)
Retiree benefits	$ 1,541	$ 1,477
Accrued employee compensation	308	263
Provisions for accrued liabilities	139	193
Inventory	650	447
Stock-based compensation	42	46
Deferred Tax Assets, Tax Credit Carryforwards	174	9
Other	59	30
Gross deferred tax assets	2,913	2,465
Less valuation allowance	(142)	(26)
Net deferred tax assets	2,771	2,439
Deferred Tax Liabilities (Table Amounts)
Goodwill	511	508
Deferred Tax Liabilities, Purchase Intangibles	346	9
Property, plant and equipment, net	518	256
Contract accounting differences	1,381	1,182
Other	29	37
Gross deferred tax liabilities	2,785	1,992
Deferred Tax Liabilities, Net	$ (14)
Total net deferred tax assets		$ 447