v3.26.1
Accumulated Other Comprehensive Income (Loss) - Changes in Each Component of Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) - USD ($)
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance $ 543,474,000 $ 388,502,000
Amounts reclassified from accumulated other comprehensive income (loss) 0 0
Net current-period other comprehensive loss (2,889,000) 1,408,000
Ending balance 552,243,000 397,434,000
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (35,522,000) (48,851,000)
Other comprehensive gain (loss) before reclassifications (3,121,000) 1,196,000
Ending balance (38,643,000) (47,655,000)
Defined Benefit Pension Items [Member]    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (4,735,000) (4,506,000)
Other comprehensive gain (loss) before reclassifications 0 212,000
Ending balance (4,735,000) (4,294,000)
Cashflow Hedge [Member]    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (58,000)  
Other comprehensive gain (loss) before reclassifications 232,000  
Ending balance 174,000  
Accumulated Other Comprehensive Income (Loss) [Member]    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Beginning balance (40,315,000) (53,357,000)
Other comprehensive gain (loss) before reclassifications (2,889,000) 1,408,000
Net current-period other comprehensive loss (2,889,000) 1,408,000
Ending balance $ (43,204,000) $ (51,949,000)