Investment Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 879,252		$ 923,415
Gross Unrealized Gains	59		70
Gross Unrealized Losses	(148,360)		(162,923)
Allowance for Credit Losses	(146)	$ (157)	(107)	$ (190)	$ (199)	$ (181)
Fair Value	730,805		760,455
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	10,765		11,099
Gross Unrealized Gains	10		11
Gross Unrealized Losses	(699)		(725)
Allowance for Credit Losses	0		0
Fair Value	10,076		10,385
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	347,134		360,683
Gross Unrealized Gains	31		57
Gross Unrealized Losses	(56,223)		(58,128)
Allowance for Credit Losses	0		0
Fair Value	290,942		302,612
Collateralized mortgage obligations, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	12,661		13,026
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(2,586)		(2,570)
Allowance for Credit Losses	0		0
Fair Value	10,075		10,456
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,048		5,094
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(741)		(747)
Allowance for Credit Losses	0		0
Fair Value	4,307		4,347
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	500,644		530,513
Gross Unrealized Gains	18		2
Gross Unrealized Losses	(87,438)		(100,400)
Allowance for Credit Losses	(25)		(7)
Fair Value	413,199		430,108
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,000		3,000
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(673)		(353)
Allowance for Credit Losses	(121)		(100)
Fair Value	$ 2,206		$ 2,547