Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	$ 7,880	$ 5,236
Other comprehensive income (loss) before reclassification, net of tax	(34)	179
Amounts reclassifed from accumulated OCI, net of tax	5	(308)
Net other comprehensive income (loss), net of tax	(29)	(129)
Accumulated other comprehensive income, ending balance	7,851	5,107
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	(367)	(284)
Other comprehensive income (loss) before reclassification, net of tax	5	(117)
Amounts reclassifed from accumulated OCI, net of tax	416	34
Net other comprehensive income (loss), net of tax	421	(83)
Accumulated other comprehensive income, ending balance	54	(367)
Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	450	272
Other comprehensive income (loss) before reclassification, net of tax	59	86
Amounts reclassifed from accumulated OCI, net of tax	(14)	(10)
Net other comprehensive income (loss), net of tax	45	76
Accumulated other comprehensive income, ending balance	495	348
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	445	(110)
Other comprehensive income (loss) before reclassification, net of tax	(98)	210
Amounts reclassifed from accumulated OCI, net of tax	21	15
Net other comprehensive income (loss), net of tax	(77)	225
Accumulated other comprehensive income, ending balance	368	115
Defined Benefit Postretirement Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	7,352	5,358
Other comprehensive income (loss) before reclassification, net of tax	0	0
Amounts reclassifed from accumulated OCI, net of tax	(418)	(347)
Net other comprehensive income (loss), net of tax	(418)	(347)
Accumulated other comprehensive income, ending balance	$ 6,934	$ 5,011