Investment Securities - Reconciliation of Available-for-Sale and Held-to-Maturity Securities in Continuous Unrealized Loss Position (Detail) $ in Thousands	Sep. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Less Than 12 Months	$ 17,587	$ 472,731
12 Months or Longer	911,924	565,777
Total	$ 929,511	$ 1,038,508
Number of Securities | security	421	439
Unrealized Losses
Less Than 12 Months	$ 93	$ 33,764
12 Months or Longer	119,107	70,254
Total	119,200	104,018
Fair Value
Less Than 12 Months	18,865	129,018
12 Months or Longer	626,390	617,633
Total	645,255	746,651
Unrealized Losses
Less Than 12 Months	585	7,192
12 Months or Longer	190,413	155,731
Total	$ 190,998	$ 162,923
Number of Securities | security	560	581
U.S. government agencies
Fair Value
Less Than 12 Months	$ 11,753	$ 114,514
12 Months or Longer	296,137	229,094
Total	$ 307,890	$ 343,608
Number of Securities | security	59	67
Unrealized Losses
Less Than 12 Months	$ 20	$ 5,856
12 Months or Longer	26,721	22,563
Total	26,741	28,419
Fair Value
Less Than 12 Months	0	6,671
12 Months or Longer	8,833	2,412
Total	8,833	9,083
Unrealized Losses
Less Than 12 Months	0	336
12 Months or Longer	690	389
Total	$ 690	$ 725
Number of Securities | security	3	3
Mortgage-backed securities, residential
Fair Value
Less Than 12 Months	$ 860	$ 127,363
12 Months or Longer	278,423	182,079
Total	$ 279,283	$ 309,442
Number of Securities | security	132	135
Unrealized Losses
Less Than 12 Months	$ 6	$ 12,399
12 Months or Longer	49,145	28,349
Total	49,151	40,748
Fair Value
Less Than 12 Months	11,286	32,549
12 Months or Longer	257,024	264,035
Total	268,310	296,584
Unrealized Losses
Less Than 12 Months	493	2,275
12 Months or Longer	70,624	55,853
Total	$ 71,117	$ 58,128
Number of Securities | security	191	182
Collateralized mortgage obligations, residential
Fair Value
Less Than 12 Months	$ 0	$ 66,316
12 Months or Longer	138,033	87,742
Total	$ 138,033	$ 154,058
Number of Securities | security	100	104
Unrealized Losses
Less Than 12 Months	$ 0	$ 3,958
12 Months or Longer	17,499	12,486
Total	17,499	16,444
Fair Value
Less Than 12 Months	0	4,668
12 Months or Longer	9,412	5,787
Total	9,412	10,455
Unrealized Losses
Less Than 12 Months	0	516
12 Months or Longer	3,062	2,054
Total	$ 3,062	$ 2,570
Number of Securities | security	11	12
Mortgage-backed securities, multifamily
Fair Value
Less Than 12 Months	$ 0	$ 0
12 Months or Longer	640	786
Total	$ 640	$ 786
Number of Securities | security	1	1
Unrealized Losses
Less Than 12 Months	$ 0	$ 0
12 Months or Longer	221	215
Total	221	215
Fair Value
Less Than 12 Months	0	2,671
12 Months or Longer	4,141	1,676
Total	4,141	4,347
Unrealized Losses
Less Than 12 Months	0	376
12 Months or Longer	883	371
Total	$ 883	$ 747
Number of Securities | security	4	4
Collateralized mortgage obligations, multifamily
Fair Value
Less Than 12 Months	$ 0	$ 37,407
12 Months or Longer	44,136	8,926
Total	$ 44,136	$ 46,333
Number of Securities | security	20	20
Unrealized Losses
Less Than 12 Months	$ 0	$ 2,861
12 Months or Longer	5,452	1,914
Total	5,452	4,775
Asset-backed securities
Fair Value
Less Than 12 Months	2,899	34,871
12 Months or Longer	42,925	17,524
Total	$ 45,824	$ 52,395
Number of Securities | security	17	17
Unrealized Losses
Less Than 12 Months	$ 27	$ 977
12 Months or Longer	830	733
Total	857	1,710
Obligations of states and political subdivisions
Fair Value
Less Than 12 Months	2,075	3,771
12 Months or Longer	16,927	16,746
Total	$ 19,002	$ 20,517
Number of Securities | security	46	46
Unrealized Losses
Less Than 12 Months	$ 40	$ 276
12 Months or Longer	1,345	713
Total	1,385	989
Fair Value
Less Than 12 Months	7,579	82,459
12 Months or Longer	344,587	341,076
Total	352,166	423,535
Unrealized Losses
Less Than 12 Months	92	3,689
12 Months or Longer	114,547	96,711
Total	$ 114,639	$ 100,400
Number of Securities | security	350	379
Corporate bonds
Fair Value
Less Than 12 Months	$ 0	$ 88,489
12 Months or Longer	94,703	22,880
Total	$ 94,703	$ 111,369
Number of Securities | security	46	49
Unrealized Losses
Less Than 12 Months	$ 0	$ 7,437
12 Months or Longer	17,894	3,281
Total	17,894	10,718
Fair Value
Less Than 12 Months	0	0
12 Months or Longer	2,393	2,647
Total	2,393	2,647
Unrealized Losses
Less Than 12 Months	0	0
12 Months or Longer	607	353
Total	$ 607	$ 353
Number of Securities | security	1	1