Securities - Company's Book Value of Pledged Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Asset Pledged as Collateral without Right [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Book value of pledged securities	$ 858,120	$ 918,523

Amount, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity), and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant