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Derivative Financial Instruments - Information about Interest Rate Swap Agreements (Detail) - USD ($) $ in Millions | 6 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jun. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Derivative [Line Items] |  |  |
Notional Amount | $ 29,755 |  | $ 26,977
Average Maturity (in years) | 2 years 2 months 12 days | 2 years 2 months 12 days |
Estimated fair value gain (loss) | $ (10) | $ 10 |
Interest Payments On Variable Rate Commercial Real Estate Loans | Cash flow hedges: |  |  |
Derivative [Line Items] |  |  |
Notional Amount | $ 25,905 |  | $ 23,977
Average Maturity (in years) | 1 year 8 months 12 days | 1 year 8 months 12 days |
Fixed | 3.41% |  | 3.45%
Variable | 5.33% |  | 5.36%
Estimated fair value gain (loss) | $ (1) | $ 11 |
Fixed Rate Long-Term Borrowings | Fair value hedges: |  |  |
Derivative [Line Items] |  |  |
Notional Amount | $ 3,850 |  | $ 3,000
Average Maturity (in years) | 5 years 7 months 6 days | 5 years 9 months 18 days |
Fixed | 3.48% |  | 3.45%
Variable | 5.53% |  | 5.62%
Estimated fair value gain (loss) | $ (9) | $ (1) |

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- Definition Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480237/815-40-50-5 + Details
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- Definition Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C + Details
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