Investment Securities - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Investment Holdings [Line Items]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (7,456,000)	$ 31,100,000
Proceeds from sale of debt securities, available-for-sale	0	0
Securities, carrying value	1,680,000,000		$ 1,340,000,000
Equity securities, at fair value	17,496,000		$ 17,283,000
Proceeds from sales of equity securities	0	0
(Gain) loss on equity securities	$ (148,000)	485,000
Redemption of funds, notice period	60 days
Unfunded commitments	$ 0
Investment in government guaranteed loans, mortgage-backed securities, small business loans	9,700,000
Charge-offs	6,640,000	0
Provision for credit loss expense	6,490,000	1,184,000
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(139,000)	(7,804,000)
Signature Bank
Investment Holdings [Line Items]
Charge-offs	6,600,000
Provision for credit loss expense	6,600,000
Financial Asset Acquired with Credit Deterioration
Investment Holdings [Line Items]
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	0	(7,634,000)
Amortization of Gain on Debt Securities Reclassified to Held to Maturity
Investment Holdings [Line Items]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	126,000	$ 135,000
Community reinvestment funds
Investment Holdings [Line Items]
Equity securities, at fair value	7,800,000
Other financial institutions
Investment Holdings [Line Items]
Unfunded commitments	$ 0

Debt Securities, Available-for-Sale, Excluding Accrued Interest, Credit Loss Expense (Reversal)

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Investment in community development loans mortgage backed securities small business loans.

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Securities pledged to secure public deposit carrying value.

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Amount, excluding accrued interest, of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from writeoff.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of cash inflow from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as investing activity.

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