Comprehensive Income/(Loss) - Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income/(Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains reclassified into earnings	$ 318	$ (537)
Provision for income taxes	(673)	7,697
Employee benefits (Non-interest expense)	12,970	12,184
Net effect on accumulated other comprehensive income/(loss) for the period	(214)	(111)
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	(86)	(59)
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	(128)	(52)
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 reclassified into earnings	(40)	0
Provision for income taxes	(46)	(59)
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	44	49
Employee benefits (Non-interest expense)	$ (172)	$ (101)