Comprehensive Income (Loss) - Components of Other Comprehensive Income (Loss) and Related Tax Effects (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss)	$ 24,444	$ (78,339)
Unrealized holding gains (losses) on available for sale securities before reclassifications
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, before tax	34,540	(111,302)
Reclassifications, before tax	164	0
OCI, after reclassifications, before tax	34,704	(111,302)
Tax effect	(10,260)	32,905
Other comprehensive income (loss)	24,444	(78,397)
Unfunded status of the supplemental retirement plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, before tax	114	63
Reclassifications, before tax	(114)	(5)
OCI, after reclassifications, before tax	0	58
Tax effect	0	0
Other comprehensive income (loss)	0	58
Amortization of prior service cost
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications, before tax	0	(7)
Amortization of actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassifications, before tax	(114)	2
Joint beneficiary agreement liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before reclassifications, before tax	0	0
Tax effect	0	0
OCI, before reclassifications, net of tax	$ 0	$ 0