Loans and Allowance for Credit Losses - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due	90 days
Default Status Of TDRs After Number Of Days Past Due	90 days
Charge-offs	$ 1,623,000	$ 3,765,000
Unfunded commitments related to nonperforming loans	200,000		$ 200,000
Off balance sheet reserve to nonperforming loans	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	25,000	0
Total gains or losses included in earnings	0	0
Recorded investment	37,467,000		55,180,000
Loans with modifications to rate and payment due to reamortization	10,000	169,000
Loans and Leases Receivable, Gross	6,952,112,000		6,839,230,000
Loans and Leases Receivable, Net of Deferred Income	$ 6,952,112,000	6,736,894,000	6,839,230,000
Forecasted Value, National Unemployment, Percent	3.87%
Financing Receivable, before Allowance for Credit Loss	$ 6,952,112,000		6,839,230,000
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery	1,100,000	3,300,000
Net Deferred Fees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	2,900,000		800,000
Unearned Premiums and Discounts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	(6,000,000)		(6,000,000)
Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 20,816,000		6,450,000
Weighted average [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecasted Value, National Unemployment, Percent	4.36%
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecasted Value, National Unemployment, Percent	4.58%
Time and Demand Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	$ 992,477,000		1,159,524,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	401,581,000		385,432,000
Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	475,000	569,000
Loans and Leases Receivable, Gross	1,123,690,000		1,173,452,000
Loans and Leases Receivable, Net of Deferred Income	1,123,690,000	1,555,671,000	1,173,452,000
Financing Receivable, before Allowance for Credit Loss	1,123,690,000		1,173,452,000
Commercial, financial, agricultural and other [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	160,000		633,000
Commercial, financial, agricultural and other [Member] | Time and Demand Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	144,000	460,000
Loans and Leases Receivable, Gross	992,477,000		1,159,524,000
Loans and Leases Receivable, Net of Deferred Income	992,477,000	1,541,280,000	1,159,524,000
Loans And Leases Receivable, Paycheck Protection Program	28,900,000		71,300,000
Financing Receivable, before Allowance for Credit Loss	992,477,000		1,159,524,000
Commercial, financial, agricultural and other [Member] | Time and Demand Loans | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	110,000		605,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	0	1,550,000
Loans and Leases Receivable, Gross	2,344,281,000		2,251,097,000
Loans and Leases Receivable, Net of Deferred Income	2,344,281,000	2,167,506,000	2,251,097,000
Financing Receivable, before Allowance for Credit Loss	2,344,281,000		2,251,097,000
Commercial Real Estate [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	15,140,000		0
Commercial Real Estate [Member] | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	0	1,000
Loans and Leases Receivable, Gross	401,581,000		385,432,000
Loans and Leases Receivable, Net of Deferred Income	401,581,000	363,604,000	385,432,000
Financing Receivable, before Allowance for Credit Loss	401,581,000		385,432,000
Commercial Real Estate [Member] | Multifamily | Financial Asset, 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 14,500,000		0
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due	150 days
Nonaccrual Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held for sale, Amount	$ 0		$ 0
Loans and Leases Receivable, Gain (Loss) on Sales, Net	$ 0	$ 0