Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 3,110,661	$ 2,743,798
Other comprehensive income before reclassifications	154,651	116,380
Current period other comprehensive income, before tax	6,920	51,249
Current period other comprehensive income, before tax	161,571	167,629
Income tax (expense)	(38,518)	(39,962)
Other comprehensive income	123,053	127,667
Ending balance	3,783,977	3,110,661
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(139,925)	(267,592)
Other comprehensive income	123,053	127,667
Ending balance	(16,872)	(139,925)
Unrealized gains/losses on AFS securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(145,589)	(255,195)
Other comprehensive income before reclassifications	136,831	92,666
Current period other comprehensive income, before tax	6,920	51,249
Current period other comprehensive income, before tax	143,751	143,915
Income tax (expense)	(34,270)	(34,309)
Other comprehensive income	109,481	109,606
Ending balance	(36,108)	(145,589)
Pension plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	5,664	(12,397)
Other comprehensive income before reclassifications	17,820	23,714
Current period other comprehensive income, before tax	0	0
Current period other comprehensive income, before tax	17,820	23,714
Income tax (expense)	(4,248)	(5,653)
Other comprehensive income	13,572	18,061
Ending balance	$ 19,236	$ 5,664