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Off-Balance Sheet Arrangements Commitments Guarantees and Contingencies (Narrative) (Detail) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Commitments And Guarantees [Line Items] |  |  |
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal) | $ 1,800 | $ (19,000) |
Credit card guarantees | 4,900 | 5,500 |
Fully collateralized credit card guarantees | 673 | 762 |
Consumer Loan [Member] |  |  |
Commitments And Guarantees [Line Items] |  |  |
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal) | 1,600 |  |
Commercial mortgage [Member] |  |  |
Commitments And Guarantees [Line Items] |  |  |
Off-Balance-Sheet, Credit Loss, Liability, Change in Method, Credit Loss Expense (Reversal) | 211 |  |
Frost Wealth Advisors [Member] |  |  |
Commitments And Guarantees [Line Items] |  |  |
Fair value of off-balance sheet managed and custody assets | $ 51,400,000 | $ 47,200,000 | $ 42,900,000

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- Definition Collateralized Credit Card Guarantees + References No definition available. + Details
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- Definition Commitments And Guarantees [Line Items] + References No definition available. + Details
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- Definition The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 + Details
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- Definition Amount of expense (reversal of expense) for expected credit loss on off-balance sheet commitment, from change in methodology. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-11 + Details
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