Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 22,317	$ 21,219
Other comprehensive income (loss) before reclassifications	(379)	1,029
Amounts reclassified into (out of) earnings	32	2
Other comprehensive income (loss)	(347)	1,031
Ending balance	24,790	22,317
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,009)	(2,040)
Ending balance	(1,356)	(1,009)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(56)	229
Other comprehensive income (loss) before reclassifications	(33)	(285)
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	(33)	(285)
Ending balance	(89)	(56)
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	103	(286)
Other comprehensive income (loss) before reclassifications	(285)	412
Amounts reclassified into (out of) earnings	7	(23)
Other comprehensive income (loss)	(278)	389
Ending balance	(175)	103
Net Unrealized Losses on Hedges of Net Investments in Non-U.S. Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(65)	95
Other comprehensive income (loss) before reclassifications	81	(160)
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	81	(160)
Ending balance	16	(65)
Other-Than-Temporary Impairment on Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6)	(9)
Other comprehensive income (loss) before reclassifications	6	3
Amounts reclassified into (out of) earnings	(2)	0
Other comprehensive income (loss)	4	3
Ending balance	(2)	(6)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(170)	(194)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified into (out of) earnings	27	24
Other comprehensive income (loss)	27	24
Ending balance	(143)	(170)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(815)	(1,875)
Other comprehensive income (loss) before reclassifications	(148)	1,059
Amounts reclassified into (out of) earnings	0	1
Other comprehensive income (loss)	(148)	1,060
Ending balance	$ (963)	$ (815)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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