Accumulated Other Comprehensive (Loss) Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 2,757,679	$ 2,618,998	$ 2,760,139	$ 2,579,757
OCI before reclassifications	(11,943)	(36,805)	(24,311)	(10,984)
Amounts reclassified from AOCI	19,474	7,010	23,267	14,195
Ending Balance	3,101,609	2,642,152	3,101,609	2,642,152
Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(290,140)	(282,095)	(274,862)	(316,231)
OCI before reclassifications	(14,199)	(31,219)	(30,864)	1,422
Amounts reclassified from AOCI	15,688	(3)	15,688	14
Ending Balance	(287,248)	(311,816)	(287,248)	(311,816)
Net Unrealized Gain (Loss) on Interest Rate Derivatives used in Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(26,587)	(61,453)	(34,783)	(61,776)
OCI before reclassifications	2,256	(5,586)	6,553	(12,406)
Amounts reclassified from AOCI	3,891	7,010	7,790	14,153
Ending Balance	(20,440)	(60,029)	(20,440)	(60,029)
Unrecognized Pension and Postretirement Plan Income (Costs)
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(2,741)	(7,444)	(2,635)	(7,469)
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	(105)	3	(211)	28
Ending Balance	(2,846)	(7,441)	(2,846)	(7,441)
Total
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(319,468)	(350,992)	(312,280)	(385,476)
Ending Balance	(310,534)	(379,286)	(310,534)	(379,286)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,403	1,501	2,790	2,979
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,403	1,501	2,790	2,979
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