Loans and Allowance for Credit Losses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 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	$ 3,370,000	$ 2,906,000	$ 7,099,000	$ 11,510,000
Unfunded commitments related to nonperforming loans	200,000		200,000		$ 200,000
Off balance sheet reserve to nonperforming loans	0		0		0
Total gains or losses included in earnings	0	0	0	0
Recorded investment	35,692,000		35,692,000		55,180,000
Loans with modifications to rate and payment due to reamortization		86,000	10,000	284,000
Loans and Leases Receivable, Gross	7,348,917,000		7,348,917,000		6,839,230,000
Loans and Leases Receivable, Net of Deferred Income	7,348,917,000	6,732,580,000	$ 7,348,917,000	6,732,580,000	6,839,230,000
Forecasted Value, National Unemployment, Percent			3.70%
Financing Receivable, before Allowance for Credit Loss	7,348,917,000		$ 7,348,917,000		6,839,230,000
Financing Receivable, Allowance for Credit Loss, Writeoff, after Recovery			5,100,000	9,500,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	0	0	0
Net Deferred Fees
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	5,200,000		5,200,000		800,000
Unearned Premiums and Discounts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Deferred Income	(5,500,000)		(5,500,000)		(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	6,029,000		$ 6,029,000		6,450,000
Weighted average [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecasted Value, National Unemployment, Percent			4.57%
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Forecasted Value, National Unemployment, Percent			4.89%
Time and Demand Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	1,012,169,000		$ 1,012,169,000		1,159,524,000
Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross	404,328,000		404,328,000		385,432,000
Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	852,000	2,066,000	1,836,000	6,522,000
Loans and Leases Receivable, Gross	1,169,206,000		1,169,206,000		1,173,452,000
Loans and Leases Receivable, Net of Deferred Income	1,169,206,000	1,224,591,000	1,169,206,000	1,224,591,000	1,173,452,000
Financing Receivable, before Allowance for Credit Loss	1,169,206,000		1,169,206,000		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	241,000		241,000		633,000
Commercial, financial, agricultural and other [Member] | Time and Demand Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	321,000	2,059,000	604,000	6,397,000
Loans and Leases Receivable, Gross	1,012,169,000		1,012,169,000		1,159,524,000
Loans and Leases Receivable, Net of Deferred Income	1,012,169,000	1,210,694,000	1,012,169,000	1,210,694,000	1,159,524,000
Loans And Leases Receivable, Paycheck Protection Program	4,900,000		4,900,000		71,300,000
Financing Receivable, before Allowance for Credit Loss	1,012,169,000		1,012,169,000		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	228,000		228,000		605,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	1,335,000	102,000	1,887,000	1,659,000
Loans and Leases Receivable, Gross	2,393,276,000		2,393,276,000		2,251,097,000
Loans and Leases Receivable, Net of Deferred Income	2,393,276,000	2,231,890,000	2,393,276,000	2,231,890,000	2,251,097,000
Financing Receivable, before Allowance for Credit Loss	2,393,276,000		2,393,276,000		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	372,000		372,000		0
Commercial Real Estate [Member] | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	0	0	411,000	1,000
Loans and Leases Receivable, Gross	404,328,000		404,328,000		385,432,000
Loans and Leases Receivable, Net of Deferred Income	404,328,000	$ 405,720,000	404,328,000	405,720,000	385,432,000
Financing Receivable, before Allowance for Credit Loss	404,328,000		404,328,000		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	73,000		$ 73,000		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		$ 0
Loans and Leases Receivable, Gain (Loss) on Sales, Net			$ 0	$ 400,000