Comprehensive Income/(Loss) - Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income/(Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities (gains) losses reclassified into earnings	$ (1,410)	$ (135)	$ (1,092)	$ (672)
Provision for income taxes	13,558	6,099	12,886	13,795
Employee benefits (Non-interest expense)	18,857	10,579	31,827	22,763
Net effect on accumulated other comprehensive income/(loss) for the period	(364)	(126)	(579)	(237)
Accumulated Unrealized Gains (Losses) on Debt Securities Available for Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net effect on accumulated other comprehensive income/(loss) for the period	(216)	(49)	(304)	(107)
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net effect on accumulated other comprehensive income/(loss) for the period	(148)	(77)	(275)	(130)
Amounts Reclassified From Accumulated Other Comprehensive Income/(Loss) [Member] | Accumulated Unrealized Gains (Losses) on Debt Securities Available for Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities (gains) losses reclassified into earnings	(9)	12	(50)	12
Provision for income taxes	(207)	(61)	(254)	(119)
Amounts Reclassified From Accumulated Other Comprehensive Income/(Loss) [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes	46	24	91	72
Employee benefits (Non-interest expense)	$ (194)	$ (101)	$ (366)	$ (202)