Investment Securities - Reconciliation of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 523,871	$ 839,272
Gross Unrealized Gains	7,758	17,806
Gross Unrealized Losses	(2,198)	(1,330)
Allowance for Credit Losses	(50)	(2)
Total securities	529,381	855,746
U.S. Treasury and U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	102,149	63,868
Gross Unrealized Gains	1,377	1,447
Gross Unrealized Losses	(555)	(313)
Allowance for Credit Losses	0	0
Total securities	102,971	65,002
Mortgage-backed securities, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	94,049	224,978
Gross Unrealized Gains	1,675	3,718
Gross Unrealized Losses	(476)	(540)
Allowance for Credit Losses	0	0
Total securities	95,248	228,156
Collateralized mortgage obligations, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	199,020	204,093
Gross Unrealized Gains	2,731	4,967
Gross Unrealized Losses	(851)	(22)
Allowance for Credit Losses	0	0
Total securities	200,900	209,038
Mortgage-backed securities, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,935	1,944
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(68)	0
Allowance for Credit Losses	0	0
Total securities	1,867	1,944
Collateralized mortgage obligations, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	34,409	39,628
Gross Unrealized Gains	798	1,909
Gross Unrealized Losses	(204)	(2)
Allowance for Credit Losses	0	0
Total securities	35,003	41,535
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	53,809	40,915
Gross Unrealized Gains	231	0
Gross Unrealized Losses	(33)	(225)
Allowance for Credit Losses	0	0
Total securities	54,007	40,690
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		228,790
Gross Unrealized Gains		5,149
Gross Unrealized Losses		(228)
Allowance for Credit Losses		(1)
Total securities		233,710
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	38,500	35,056
Gross Unrealized Gains	946	616
Gross Unrealized Losses	(11)	0
Allowance for Credit Losses	(50)	(1)
Total securities	$ 39,385	$ 35,671

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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