Derivative instruments - Hedged Items in Fair Value Hedging Relationships (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Long-term debt \| Fair value hedging
Derivative [Line Items]
Carrying amount of hedged asset or liability, Long-term debt	$ 21,416	$ 22,447
Hedge accounting basis adjustment increase (decrease), Long-term debt	(833)	183
Hedged liability, discontinued fair value hedge, cumulative decrease	56	72
Securities – Available-for-sale \| Fair value hedging
Derivative [Line Items]
Carrying amount of hedged asset or liability, Available-for-sale securities	30,383	24,400
Hedge accounting basis adjustment increase (decrease), Available-for-sale securities	(1,764)	590
Hedge accounting basis adjustment increase (decrease), discontinued hedges	104	165
Not designated as hedging \| Securities – Available-for-sale \| Foreign exchange contracts
Derivative [Line Items]
Hedged financial instruments, carrying amount	$ 125	$ 141

Hedged Financial Instruments, Carrying Amount

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+ References

No definition available.

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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- Definition

Amount of asset hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

+ References

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- Definition

Amount of liability hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL109999712-113959

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