v3.26.3
Other Comprehensive Income (Loss) - Components of AOCI (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance $ 2,906,985 $ 2,707,555 $ 2,833,212 $ 2,601,207
Current - period other comprehensive income (loss) (83,007) 16,527 (98,757) 48,112
Ending balance 2,864,491 2,767,035 2,864,491 2,767,035
Accumulated Other Comprehensive (Loss)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance (91,933) (103,770) (76,183) (135,355)
Current - period other comprehensive income (loss) (83,007) 16,527 (98,757) 48,112
Ending balance (174,940) (87,243) (174,940) (87,243)
Unrealized Losses on Available for Sale Debt Securities        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance (97,856) (108,692) (77,178) (144,561)
Current - period other comprehensive income (loss) (86,518) 19,948 (107,196) 55,817
Ending balance (184,374) (88,744) (184,374) (88,744)
Post- Retirement Obligations        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 2,702 5,488 2,854 6,147
Current - period other comprehensive income (loss) (135) (2,388) (287) (3,047)
Ending balance 2,567 3,100 2,567 3,100
Unrealized Gains on Derivatives (cash flow hedges)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 3,221 (566) (1,859) 3,059
Current - period other comprehensive income (loss) 3,646 (1,033) 8,726 (4,658)
Ending balance $ 6,867 $ (1,599) $ 6,867 $ (1,599)