Investment Securities - Reconciliation of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 981,126	$ 839,272
Gross Unrealized Gains	13,645	17,806
Gross Unrealized Losses	(6,077)	(1,330)
Allowance for Credit Losses	(21)	(2)
Total securities	988,673	855,746
U.S. Treasury and U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	105,385	63,868
Gross Unrealized Gains	1,655	1,447
Gross Unrealized Losses	(596)	(313)
Allowance for Credit Losses	0	0
Total securities	106,444	65,002
Mortgage-backed securities, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	315,852	224,978
Gross Unrealized Gains	2,380	3,718
Gross Unrealized Losses	(3,364)	(540)
Allowance for Credit Losses	0	0
Total securities	314,868	228,156
Collateralized mortgage obligations, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	184,683	204,093
Gross Unrealized Gains	3,555	4,967
Gross Unrealized Losses	(312)	(22)
Allowance for Credit Losses	0	0
Total securities	187,926	209,038
Mortgage-backed securities, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,938	1,944
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(38)	0
Allowance for Credit Losses	0	0
Total securities	1,900	1,944
Collateralized mortgage obligations, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,910	39,628
Gross Unrealized Gains	999	1,909
Gross Unrealized Losses	(30)	(2)
Allowance for Credit Losses	0	0
Total securities	29,879	41,535
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	47,189	40,915
Gross Unrealized Gains	102	0
Gross Unrealized Losses	(55)	(225)
Allowance for Credit Losses	0	0
Total securities	47,236	40,690
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	263,114	228,790
Gross Unrealized Gains	3,813	5,149
Gross Unrealized Losses	(1,673)	(228)
Allowance for Credit Losses	(3)	(1)
Total securities	265,251	233,710
Debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	34,055	35,056
Gross Unrealized Gains	1,141	616
Gross Unrealized Losses	(9)	0
Allowance for Credit Losses	(18)	(1)
Total securities	$ 35,169	$ 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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