Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ 7,435,127	$ 6,701,391
Other comprehensive income before reclassification	27,212	(10,205)
Amounts reclassified to earnings	(130)	(187)
Other comprehensive income (loss) , net	27,082	(10,392)
Ending balance	7,499,897	6,727,139
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(155,334)	(146,456)
Ending balance	(128,252)	(156,848)
Unrealized Gains and Losses on AFS Securities
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(133,898)	(115,502)
Other comprehensive income before reclassification	27,212	(10,205)
Amounts reclassified to earnings	0	0
Other comprehensive income (loss) , net	27,212	(10,205)
Ending balance	(106,686)	(125,707)
Unrealized Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss)
Beginning balance	1,245	2,114
Other comprehensive income before reclassification	0	0
Amounts reclassified to earnings	(218)	(222)
Other comprehensive income (loss) , net	(218)	(222)
Ending balance	1,027	1,892
Defined Benefit Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(22,681)	(33,068)
Other comprehensive income before reclassification	0	0
Amounts reclassified to earnings	88	35
Other comprehensive income (loss) , net	88	35
Ending balance	$ (22,593)	$ (33,033)