Derivative Instruments - Summary of Cumulative Hedging Adjustments and the Carrying Amount of Assets and Liabilities Designated in Fair Value Hedges (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Available-for-sale Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative hedging adjustment asset related to discontinued hedging relationships	$ (6)
Long-term Debt Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative hedging adjustment related to discontinued hedging relationships	$ 700	$ 726

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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 http://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, remaining after discontinued hedge.

+ References

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