Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 21,103	$ 21,328	$ 20,248
Other comprehensive income (loss)	(598)	(935)	(412)
Ending balance	21,219	21,103	21,328
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,442)	(507)	(95)
Other comprehensive income (loss) before reclassifications	(589)	(1,012)
Amounts reclassified into (out of) earnings	(9)	77
Other comprehensive income (loss)	(598)	(935)	(412)
Ending balance	(2,040)	(1,442)	(507)
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	(64)	20
Amounts reclassified into (out of) earnings	0	(3)
Other comprehensive income (loss)	(64)	17
Ending balance	229	293	276
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	(164)	(314)
Amounts reclassified into (out of) earnings	6	(6)
Other comprehensive income (loss)	(158)	(320)
Ending balance	(286)	(128)	192
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	109	0
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	109	0
Ending balance	95	(14)	(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	8	15
Amounts reclassified into (out of) earnings	(1)	(2)
Other comprehensive income (loss)	7	13
Ending balance	(9)	(16)	(29)
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	0	1
Amounts reclassified into (out of) earnings	(11)	88
Other comprehensive income (loss)	(11)	89
Ending balance	(194)	(183)	(272)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,394)	(660)
Other comprehensive income (loss) before reclassifications	(478)	(734)
Amounts reclassified into (out of) earnings	(3)	0
Other comprehensive income (loss)	(481)	(734)
Ending balance	$ (1,875)	$ (1,394)	$ (660)