Income Taxes (Details 5) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Deferred Tax Assets
Retirement benefits	$ 1,819	$ 1,337
Provisions for accrued liabilities	649	686
Stock-based compensation	130	91
Other	78	10
Gross deferred tax assets	2,676	2,124
Less valuation allowance	(50)	0
Net deferred tax assets	2,626	2,124
Deferred Tax Liabilities
Goodwill amortization	716	692
Depreciation and amortization	277	143
Contract accounting differences	218	255
Purchased intangibles	19	14
Gross deferred tax liabilities	1,230	1,104
Total net deferred tax assets	$ 1,396	$ 1,020