Fair value measurements - Mortgage Servicing Rights Fair Value Measurement Inputs (Detail) $ in Thousands	Mar. 31, 2026 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Impact on fair value of 10% adverse change	$ (16,000)
Impact on fair value of 20% adverse change	(30,000)
Impact on fair value of 10% adverse change	(15,000)
Impact on fair value of 20% adverse change	$ (29,000)
Prepayment Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0744
Credit Spread
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.0722
Minimum \| Prepayment Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.06
Minimum \| Credit Spread
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.05
Maximum \| Prepayment Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.17
Maximum \| Credit Spread
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Measurement input	0.20

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.

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The hypothetical financial impact of a 10 percent adverse change of the specified assumption on the fair value of transferor's interests in transferred financial assets (including any servicing assets or servicing liabilities) as of the balance sheet date.

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Value of input used to measure servicing asset.

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