Investment Securities - Reconciliation of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 935,099		$ 825,137
Gross Unrealized Gains	20		2,046
Gross Unrealized Losses	(181,402)		(11,791)
Allowance for Credit Losses	(152)	$ (190)	(181)	$ (183)	$ (137)	$ 0
Fair Value	753,565		815,211
U.S. government agencies
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	16,296		18,672
Gross Unrealized Gains	13		293
Gross Unrealized Losses	(733)		0
Allowance for Credit Losses	0		0
Fair Value	15,576		18,965
Mortgage-backed securities, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	357,453		370,247
Gross Unrealized Gains	5		718
Gross Unrealized Losses	(61,970)		(5,989)
Allowance for Credit Losses	0		0
Fair Value	295,488		364,976
Collateralized mortgage obligations, residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	13,328		13,921
Gross Unrealized Gains	0		168
Gross Unrealized Losses	(2,380)		0
Allowance for Credit Losses	0		0
Fair Value	10,948		14,089
Mortgage-backed securities, multifamily
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,117		2,710
Gross Unrealized Gains	0		26
Gross Unrealized Losses	(768)		(2)
Allowance for Credit Losses	0		0
Fair Value	4,349		2,734
Obligations of states and political subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	539,905		416,587
Gross Unrealized Gains	2		810
Gross Unrealized Losses	(115,168)		(5,800)
Allowance for Credit Losses	(17)		(21)
Fair Value	424,722		411,576
Corporate bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,000		3,000
Gross Unrealized Gains	0		31
Gross Unrealized Losses	(383)		0
Allowance for Credit Losses	(135)		(160)
Fair Value	$ 2,482		$ 2,871