Income Taxes (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]
Unrecognized tax benefits	$ 5,340	$ 5,230
Portion that, if recognized, would reduce tax expense and effective tax rate	4,032	3,938
Accrued interest on unrecognized tax benefits	1,051	1,033
Accrued penalties on unrecognized tax benefits	135	121
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months lower limit	0	0
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months upper limit	500	900
Lower Limit [Member]
Income Tax Disclosure [Line Items]
Portion that, if recognized, would reduce tax expense and effective tax rate	0	0
Upper Limit [Member]
Income Tax Disclosure [Line Items]
Portion that, if recognized, would reduce tax expense and effective tax rate	$ 400	$ 500