Income Taxes (Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Unrecognized Tax Benefits
Unrecognized tax benefits	$ 3,223	$ 3,106	$ 2,932
Portion that, if recognized, would reduce tax expense and effective tax rate	2,346	2,253
Accrued interest on unrecognized tax benefits	570	559
Accrued penalties on unrecognized tax benefits	97	101
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	800	400
Lower Limit [Member]
Unrecognized Tax Benefits
Portion that, if recognized, would reduce tax expense and effective tax rate	0	0
Upper Limit [Member]
Unrecognized Tax Benefits
Portion that, if recognized, would reduce tax expense and effective tax rate	$ 250	$ 350