Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 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	273	528
Amounts reclassifed from accumulated OCI, net of tax	(227)	(482)
Net other comprehensive income (loss), net of tax	46	46
Accumulated other comprehensive income, ending balance	7,926	5,282
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	(29)	(153)
Amounts reclassifed from accumulated OCI, net of tax	416	34
Net other comprehensive income (loss), net of tax	387	(119)
Accumulated other comprehensive income, ending balance	20	(403)
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	30	155
Amounts reclassifed from accumulated OCI, net of tax	(15)	(13)
Net other comprehensive income (loss), net of tax	15	142
Accumulated other comprehensive income, ending balance	465	414
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	272	526
Amounts reclassifed from accumulated OCI, net of tax	29	22
Net other comprehensive income (loss), net of tax	301	548
Accumulated other comprehensive income, ending balance	746	438
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	(657)	(525)
Net other comprehensive income (loss), net of tax	(657)	(525)
Accumulated other comprehensive income, ending balance	$ 6,695	$ 4,833