Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	$ 5,334	$ 8,061
Other comprehensive income (loss) before reclassification, net of tax	(110)	(600)
Amounts reclassifed from accumulated OCI, net of tax	(410)	(421)
Net other comprehensive income (loss), net of tax	(520)	(1,021)
Accumulated other comprehensive income, ending balance	4,814	7,040
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	(1,198)	(26)
Other comprehensive income (loss) before reclassification, net of tax	174	(185)
Amounts reclassifed from accumulated OCI, net of tax	0	0
Net other comprehensive income (loss), net of tax	174	(185)
Accumulated other comprehensive income, ending balance	(1,024)	(211)
Net Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	484	499
Other comprehensive income (loss) before reclassification, net of tax	(21)	34
Amounts reclassifed from accumulated OCI, net of tax	0	(9)
Net other comprehensive income (loss), net of tax	(21)	25
Accumulated other comprehensive income, ending balance	463	524
Net Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	16	741
Other comprehensive income (loss) before reclassification, net of tax	(263)	(449)
Amounts reclassifed from accumulated OCI, net of tax	19	17
Net other comprehensive income (loss), net of tax	(244)	(432)
Accumulated other comprehensive income, ending balance	(228)	309
Defined Benefit Postretirement Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income, beginning balance	6,032	6,847
Other comprehensive income (loss) before reclassification, net of tax	0	0
Amounts reclassifed from accumulated OCI, net of tax	(429)	(429)
Net other comprehensive income (loss), net of tax	(429)	(429)
Accumulated other comprehensive income, ending balance	$ 5,603	$ 6,418