Stockholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 21,328	$ 20,248	$ 20,825
Other comprehensive income (loss) before reclassifications	(1,012)	(338)
Amounts reclassified into (out of) earnings	77	(74)
Other comprehensive income (loss)	(935)	(412)	(455)
Ending balance	21,103	21,328	20,248
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(507)	(95)	360
Other comprehensive income (loss)	(935)	(412)	(455)
Ending balance	(1,442)	(507)	(95)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	276	161
Other comprehensive income (loss) before reclassifications	20	112
Amounts reclassified into (out of) earnings	(3)	3
Other comprehensive income (loss)	17	115
Ending balance	293	276	161
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	192	(221)
Other comprehensive income (loss) before reclassifications	(314)	422
Amounts reclassified into (out of) earnings	(6)	(9)
Other comprehensive income (loss)	(320)	413
Ending balance	(128)	192	(221)
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	0	0
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	0	0
Ending balance	(14)	(14)	(14)
Other-Than-Temporary Impairment on Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(29)	(47)
Other comprehensive income (loss) before reclassifications	15	17
Amounts reclassified into (out of) earnings	(2)	1
Other comprehensive income (loss)	13	18
Ending balance	(16)	(29)	(47)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(272)	(203)
Other comprehensive income (loss) before reclassifications	1	0
Amounts reclassified into (out of) earnings	88	(69)
Other comprehensive income (loss)	89	(69)
Ending balance	(183)	(272)	(203)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(660)	229
Other comprehensive income (loss) before reclassifications	(734)	(889)
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	(734)	(889)
Ending balance	$ (1,394)	$ (660)	$ 229