Accumulated Other Comprehensive (Loss) Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 3,101,609	$ 2,642,152	$ 2,760,139	$ 2,579,757
OCI before reclassifications	61,936	(101,399)	37,625	(112,383)
Amounts reclassified from AOCI	3,874	6,435	27,141	20,630
Ending Balance	3,203,943	2,566,693	3,203,943	2,566,693
Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(287,248)	(311,816)	(274,862)	(316,231)
OCI before reclassifications	68,560	(105,050)	37,696	(103,628)
Amounts reclassified from AOCI	1	0	15,689	14
Ending Balance	(217,265)	(415,372)	(217,265)	(415,372)
Net Unrealized Gain (Loss) on Interest Rate Derivatives used in Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(20,440)	(60,029)	(34,783)	(61,776)
OCI before reclassifications	(6,624)	3,651	(71)	(8,755)
Amounts reclassified from AOCI	3,979	6,420	11,769	20,573
Ending Balance	(23,085)	(49,958)	(23,085)	(49,958)
Unrecognized Pension and Postretirement Plan Income (Costs)
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,846)	(7,441)	(2,635)	(7,469)
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	(106)	15	(317)	43
Ending Balance	(2,952)	(7,426)	(2,952)	(7,426)
Total
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(310,534)	(379,286)	(312,280)	(385,476)
Ending Balance	(243,302)	(472,756)	(243,302)	(472,756)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,422	1,494	4,212	4,473
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,422	1,494	4,212	4,473
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized Gain (Loss) on Interest Rate Derivatives used in Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	0	0	0	0
Reclassification out of Accumulated Other Comprehensive Income | Unrecognized Pension and Postretirement Plan Income (Costs)
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	$ 0	$ 0	$ 0	$ 0