Shareholders' Equity - Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 26,200	$ 24,431
Other comprehensive income (loss) before reclassifications	(628)	(62)
Amounts reclassified into (out of) earnings	23	18
Other comprehensive income (loss)	(605)	(44)
Ending balance	25,005	23,861
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	187	(876)
Other comprehensive income (loss)	(605)	(44)
Ending balance	(418)	(920)
Net Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	57	(70)
Other comprehensive income (loss) before reclassifications	(15)	112
Amounts reclassified into (out of) earnings	15	5
Other comprehensive income (loss)	0	117
Ending balance	57	47
Net Unrealized Gains (Losses) on Available-for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	848	409
Other comprehensive income (loss) before reclassifications	(413)	126
Amounts reclassified into (out of) earnings	0	1
Other comprehensive income (loss)	(413)	127
Ending balance	435	536
Net Unrealized Losses on Hedges of Net Investments in Non-U.S. Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(204)	46
Other comprehensive income (loss) before reclassifications	135	108
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	135	108
Ending balance	(69)	154
Other-Than-Temporary Impairment on Held-to-Maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2)	(2)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	0	0
Ending balance	(2)	(2)
Net Unrealized Losses on Retirement Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(178)	(187)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified into (out of) earnings	8	12
Other comprehensive income (loss)	8	12
Ending balance	(170)	(175)
Foreign Currency Translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(334)	(1,072)
Other comprehensive income (loss) before reclassifications	(335)	(408)
Amounts reclassified into (out of) earnings	0	0
Other comprehensive income (loss)	(335)	(408)
Ending balance	$ (669)	$ (1,480)

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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