Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	$ 8,061	$ 7,880
Other comprehensive income (loss) before reclassification, net of tax	(2,145)	273
Amounts reclassifed from accumulated OCI, net of tax	(622)	(227)
Net other comprehensive income (loss), net of tax	(2,767)	46
Accumulated other comprehensive income, ending balance	5,294	7,926
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	(26)	(367)
Other comprehensive income (loss) before reclassification, net of tax	(1,204)	(29)
Amounts reclassifed from accumulated OCI, net of tax	0	416
Net other comprehensive income (loss), net of tax	(1,204)	387
Accumulated other comprehensive income, ending balance	(1,230)	20
Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	499	450
Other comprehensive income (loss) before reclassification, net of tax	(51)	30
Amounts reclassifed from accumulated OCI, net of tax	(6)	(15)
Net other comprehensive income (loss), net of tax	(57)	15
Accumulated other comprehensive income, ending balance	442	465
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	741	445
Other comprehensive income (loss) before reclassification, net of tax	(890)	272
Amounts reclassifed from accumulated OCI, net of tax	28	29
Net other comprehensive income (loss), net of tax	(862)	301
Accumulated other comprehensive income, ending balance	(121)	746
Defined Benefit Postretirement Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	6,847	7,352
Other comprehensive income (loss) before reclassification, net of tax	0	0
Amounts reclassifed from accumulated OCI, net of tax	(644)	(657)
Net other comprehensive income (loss), net of tax	(644)	(657)
Accumulated other comprehensive income, ending balance	$ 6,203	$ 6,695