Investment Securities - Reconciliation of Available-for-Sale Securities (Detail) $ in Thousands	Sep. 30, 2023 USD ($) security	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($) security	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,061,596		$ 1,158,534
Gross Unrealized Gains	114		106
Gross Unrealized Losses	(119,200)		(104,018)
Allowance for Credit Losses	0	$ 0	(310)	$ (4,165)	$ (2,802)	$ (83)
Total	942,510		1,054,312
Less Than 12 Months	18,865		129,018
Less Than 12 Months	585		7,192
12 Months or Longer	626,390		617,633
12 Months or Longer	$ 190,413		$ 155,731
Number of Securities | security	560		581
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 645,255		$ 746,651
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	190,998		162,923
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	347,515		383,958
Gross Unrealized Gains	114		100
Gross Unrealized Losses	(26,741)		(28,419)
Allowance for Credit Losses	0		0
Total	320,888		355,639
Less Than 12 Months	0		6,671
Less Than 12 Months	0		336
12 Months or Longer	8,833		2,412
12 Months or Longer	$ 690		$ 389
Number of Securities | security	3		3
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 8,833		$ 9,083
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	690		725
Mortgage-backed securities, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	328,434		351,355
Gross Unrealized Gains	0		6
Gross Unrealized Losses	(49,151)		(40,748)
Allowance for Credit Losses	0		0
Total	279,283		310,613
Less Than 12 Months	11,286		32,549
Less Than 12 Months	493		2,275
12 Months or Longer	257,024		264,035
12 Months or Longer	$ 70,624		$ 55,853
Number of Securities | security	191		182
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 268,310		$ 296,584
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	71,117		58,128
Collateralized mortgage obligations, residential
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	155,532		170,502
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(17,499)		(16,444)
Allowance for Credit Losses	0		0
Total	138,033		154,058
Less Than 12 Months	0		4,668
Less Than 12 Months	0		516
12 Months or Longer	9,412		5,787
12 Months or Longer	$ 3,062		$ 2,054
Number of Securities | security	11		12
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 9,412		$ 10,455
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	3,062		2,570
Mortgage-backed securities, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	861		1,000
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(221)		(215)
Allowance for Credit Losses	0		0
Total	640		785
Less Than 12 Months	0		2,671
Less Than 12 Months	0		376
12 Months or Longer	4,141		1,676
12 Months or Longer	$ 883		$ 371
Number of Securities | security	4		4
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 4,141		$ 4,347
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	883		747
Collateralized mortgage obligations, multifamily
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	49,588		51,108
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(5,452)		(4,775)
Allowance for Credit Losses	0		0
Total	44,136		46,333
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	46,681		54,105
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(857)		(1,710)
Allowance for Credit Losses	0		0
Total	45,824		52,395
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	20,387		22,112
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(1,385)		(989)
Allowance for Credit Losses	0		(1)
Total	19,002		21,122
Less Than 12 Months	7,579		82,459
Less Than 12 Months	92		3,689
12 Months or Longer	344,587		341,076
12 Months or Longer	$ 114,547		$ 96,711
Number of Securities | security	350		379
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 352,166		$ 423,535
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	114,639		100,400
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	112,598		124,394
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(17,894)		(10,718)
Allowance for Credit Losses	0		(309)
Total	94,704		113,367
Less Than 12 Months	0		0
Less Than 12 Months	0		0
12 Months or Longer	2,393		2,647
12 Months or Longer	$ 607		$ 353
Number of Securities | security	1		1
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value	$ 2,393		$ 2,647
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Accumulated Loss	$ 607		$ 353