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Commitments, Contingencies and Guarantees - Notional Amount of Off-Balance Sheet Financial Instruments (Detail) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
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Commitments to extend credit for loans (excluding credit card loans) [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | $ 18,049,199 | $ 17,819,711
Commitments to extend credit under credit card loans [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | 5,163,320 | 5,994,640
Commercial letters of credit [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | 2,144 | 217
Standby letters of credit [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | 483,578 | 468,384
Forward contracts [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | 151,279 | 119,978
Spot foreign exchange contracts [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | 67,479 | 34,233
Commitments to extend credit for securities purchased under agreements to resell [Member] |  |
Commitments and Contingencies Disclosure [Line Items] |  |
Contractual or notional amount of off-balance sheet financial instruments | $ 876,000 | $ 191,000

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