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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities losses (gains) reclassified into earnings	$ (135)	$ (205)	$ (672)	$ (350)
Provision for income taxes	6,099	9,063	13,795	19,005
Employee benefits (Non-interest expense)	10,579	11,511	22,763	23,570
Net effect on accumulated other comprehensive income/(loss) for the period	(126)	81	(237)	270
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	(49)	6	(107)	120
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	(77)	75	(130)	150
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 losses (gains) reclassified into earnings	12	8	12	159
Provision for income taxes	(61)	(2)	(119)	(39)
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	24	(24)	72	(48)
Employee benefits (Non-interest expense)	$ (101)	$ 99	$ (202)	$ 198