Derivatives - Derivatives Designated as Cash Flow and Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Cash flow hedges
Amounts excluded from effectiveness testing and recognized in other income	$ 30	$ 53
Cash flow hedges
Cash flow hedges
Gains (Losses) in Accumulated OCI on Derivatives	509	254
Gains (Losses) in Income Reclassified from Accumulated OCI	(26)	(23)
Interest rate risk on variable-rate assets \| Cash flow hedges
Cash flow hedges
Gains (Losses) in Accumulated OCI on Derivatives	591	254
Gains (Losses) in Income Reclassified from Accumulated OCI	(26)	(23)
Price risk on certain compensation plans \| Cash flow hedges
Cash flow hedges
Gains (Losses) in Accumulated OCI on Derivatives	(82)	0
Gains (Losses) in Income Reclassified from Accumulated OCI	0	0
Foreign exchange risk \| Net investment hedges
Cash flow hedges
Gains (Losses) in Accumulated OCI on Derivatives	1,368	6
Gains (Losses) in Income Reclassified from Accumulated OCI	$ 0	$ 1

Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), After Reclassification And Tax [Abstract]

No definition available.

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- Definition

The net gain (loss) relating to components of the gain (loss) on the cash flow hedging instrument excluded from the assessment of cash flow hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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- Definition

Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580

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- Definition

Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e637-108580

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