v3.26.3
Comprehensive Income/(Loss) - Schedule of Amounts Reclassified from Accumulated Other Comprehensive Income/(Loss) (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]        
Net securities gains reclassified into earnings $ 151 $ (1,210) $ (1,480) $ (2,302)
Provision for income taxes 23,710 19,737 71,345 32,623
Amortization of state tax rate change reclassified into earnings (243) (209) (730) (477)
Employee benefits (Non-interest expense) 14,853 18,040 51,613 49,867
Net effect on accumulated other comprehensive income/(loss) for the period (523) (389) (1,574) (967)
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 (291) (248) (884) (551)
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 (232) (141) (690) (416)
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 (62) (55) (200) (104)
Provision for income taxes 14 16 46 30
Amortization of state tax rate change reclassified into earnings (243) (209) (730) (477)
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 70 45 206 136
Employee benefits (Non-interest expense) $ (302) $ (186) $ (896) $ (552)