v3.26.1
Other Comprehensive Income (Loss) - Components of AOCI (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance $ 2,862,869 $ 2,658,794 $ 2,833,212 $ 2,601,207
Current - period other comprehensive income (loss) (5,510) 6,476 (15,750) 31,585
Ending balance 2,906,985 2,707,555 2,906,985 2,707,555
Accumulated Other Comprehensive (Loss)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance (86,423) (110,246) (76,183) (135,355)
Current - period other comprehensive income (loss) (5,510) 6,476 (15,750) 31,585
Ending balance (91,933) (103,770) (91,933) (103,770)
Unrealized Losses on Available for Sale Debt Securities        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance (89,867) (117,837) (77,178) (144,561)
Current - period other comprehensive income (loss) (7,989) 9,145 (20,678) 35,869
Ending balance (97,856) (108,692) (97,856) (108,692)
Post- Retirement Obligations        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 2,837 5,817 2,854 6,147
Current - period other comprehensive income (loss) (135) (329) (152) (659)
Ending balance 2,702 5,488 2,702 5,488
Unrealized Gains on Derivatives (cash flow hedges)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 607 1,774 (1,859) 3,059
Current - period other comprehensive income (loss) 2,614 (2,340) 5,080 (3,625)
Ending balance $ 3,221 $ (566) $ 3,221 $ (566)