Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred Tax Assets (Table Amounts)
Retiree benefits	$ 2,745	$ 1,308
Accrued employee compensation	311	333
Provisions for accrued liabilities	392	313
Stock-based compensation	91	109
Other	104us-gaap_DeferredTaxAssetsOther	144us-gaap_DeferredTaxAssetsOther
Gross deferred tax assets	3,643us-gaap_DeferredTaxAssetsGross	2,207us-gaap_DeferredTaxAssetsGross
Less valuation allowance	(53)	(55)
Net deferred tax assets	3,590us-gaap_DeferredTaxAssetsNet	2,152us-gaap_DeferredTaxAssetsNet
Deferred Tax Liabilities (Table Amounts)
Goodwill	787	806
Property, plant and equipment, net	315	348
Contract accounting differences	332	134
Other	130us-gaap_DeferredTaxLiabilitiesOther	50us-gaap_DeferredTaxLiabilitiesOther
Gross deferred tax liabilities	1,564us-gaap_DeferredIncomeTaxLiabilities	1,338us-gaap_DeferredIncomeTaxLiabilities
Total net deferred tax assets	$ 2,026us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 814us-gaap_DeferredTaxAssetsLiabilitiesNet

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