Investment Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 827,253	$ 836,523
Gross Unrealized Gains	36	132
Gross Unrealized Losses	(145,286)	(133,946)
Allowance for Credit Losses	(146)	(146)	$ (157)	$ (107)
Fair Value	681,857	702,563
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,270	10,406
Gross Unrealized Gains	6	7
Gross Unrealized Losses	(499)	(499)
Allowance for Credit Losses	0	0
Fair Value	9,777	9,914
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	326,731	332,509
Gross Unrealized Gains	5	82
Gross Unrealized Losses	(57,889)	(52,165)
Allowance for Credit Losses	0	0
Fair Value	268,847	280,426
Collateralized mortgage obligations, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	12,079	12,243
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,878)	(2,796)
Allowance for Credit Losses	0	0
Fair Value	9,201	9,447
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	4,126	4,145
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(677)	(651)
Allowance for Credit Losses	0	0
Fair Value	3,449	3,494
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	471,047	474,220
Gross Unrealized Gains	25	43
Gross Unrealized Losses	(82,520)	(77,379)
Allowance for Credit Losses	(25)	(25)
Fair Value	388,527	396,859
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,000	3,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(823)	(456)
Allowance for Credit Losses	(121)	(121)
Fair Value	$ 2,056	$ 2,423