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Derivative financial instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2026 | Dec. 31, 2025
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | $ 242,000 | $ 245,000
Subject to master netting agreements | 503,000 | 454,000
Reduction in estimated fair value of interest rate contracts in asset position | (366,000) | (341,000)
Reduction in estimated fair value of interest rate contracts in liability position | (6,000) | (32,000)
Fair value hedges: |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 218,000 | 190,000
Subject to master netting agreements | 476,000 | 409,000
Fair value hedges: | Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 0 | 1,000
Subject to master netting agreements | 18,000 | 16,000
Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 24,000 | 54,000
Subject to master netting agreements | 9,000 | 29,000
Interest rate swap agreements | Fair value hedges: | Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 0 | 0
Subject to master netting agreements | 17,000 | 15,000
Commitments to sell real estate loans | Fair value hedges: | Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 0 | 1,000
Subject to master netting agreements | 1,000 | 1,000
Commitments to sell real estate loans | Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 8,000 | 24,000
Subject to master netting agreements | 2,000 | 6,000
Commitments to originate real estate loans for sale | Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 9,000 | 17,000
Subject to master netting agreements | 4,000 | 21,000
Interest Rate Contract For Real Estate Loans | Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 7,000 | 13,000
Subject to master netting agreements | 3,000 | 2,000
Interest Rate Contracts | Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 196,000 | 173,000
Subject to master netting agreements | 456,000 | 394,000
Foreign exchange and other option and futures contracts | Fair value hedges: | Not Designated as Hedging Instrument |  |
Derivatives, Fair Value [Line Items] |  |
Subject to master netting agreements | 22,000 | 17,000
Subject to master netting agreements | $ 20,000 | $ 15,000

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