Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Termination Benefits [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 145	$ 13	$ 44
Additions (deductions) charged (credited) to expense		235	(12)
Payments	(82)	(103)	(19)
Ending Balance	63	145	13
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	239	293	275
Additions (reductions) to expense	4	(13)	92
Bad debt write-offs	(76)	(41)	(74)
Ending Balance	167	239	293
Deferred Income Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	9,185	7,921	7,535
Reduction of deferred income tax expense	(305)	(190)	(1,818)
Additions to deferred income tax expense	2,216	1,454	2,204
Ending Balance	$ 11,096	$ 9,185	$ 7,921