Stockholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 21,103	$ 21,328
Other comprehensive income (loss) before reclassifications	442	(517)
Amounts reclassified into (out of) earnings	3	13
Other comprehensive income (loss)	445	(504)
Ending balance	22,073	21,347
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,442)	(507)
Other comprehensive income (loss)	445	(504)
Ending balance	(997)	(1,011)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	293	276
Other comprehensive income (loss) before reclassifications	(174)	19
Amounts reclassified into (out of) earnings	0	1
Other comprehensive income (loss)	(174)	20
Ending balance	119	296
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(128)	192
Other comprehensive income (loss) before reclassifications	522	(134)
Amounts reclassified into (out of) earnings	2	(2)
Other comprehensive income (loss)	524	(136)
Ending balance	396	56
Net Unrealized Losses on Hedges of Net Investments in Non-U.S. Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(14)	(14)
Other comprehensive income (loss) before reclassifications	51	0
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	51	0
Ending balance	37	(14)
Other-Than-Temporary Impairment on Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(16)	(29)
Other comprehensive income (loss) before reclassifications	4	8
Amounts reclassified into (out of) earnings	(1)	(1)
Other comprehensive income (loss)	3	7
Ending balance	(13)	(22)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(183)	(272)
Other comprehensive income (loss) before reclassifications	(4)	0
Amounts reclassified into (out of) earnings	2	15
Other comprehensive income (loss)	(2)	15
Ending balance	(185)	(257)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,394)	(660)
Other comprehensive income (loss) before reclassifications	43	(410)
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	43	(410)
Ending balance	$ (1,351)	$ (1,070)