Accumulated Other Comprehensive (Loss) Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 2,471,093	$ 2,692,958	$ 2,712,680	$ 2,616,828
OCI before reclassifications	(120,385)	(21,622)	(362,596)	(16,073)
Amounts reclassified from AOCI	(20,005)	(601)	(61,738)	(25,557)
Ending Balance	2,471,159	2,699,818	2,471,159	2,699,818
Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(249,427)	62,769	40,440	81,604
OCI before reclassifications	(120,385)	(21,622)	(362,596)	(16,073)
Amounts reclassified from AOCI	(41)	0	(20)	(25,901)
Ending Balance	(368,200)	41,784	(368,200)	41,784
Net Unrealized (Loss) Gain on Interest Rate Swaps used in Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(46,620)	367	(4,816)	0
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	(19,989)	(891)	(61,793)	(524)
Ending Balance	(66,609)	(524)	(66,609)	(524)
Unrecognized Pension and Postretirement Plan Income (Costs)
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(8,163)	(15,935)	(8,213)	(16,513)
OCI before reclassifications	0	0	0	0
Amounts reclassified from AOCI	25	290	75	868
Ending Balance	(8,138)	(15,645)	(8,138)	(15,645)
Total
Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(304,210)	47,201	27,411	65,091
Ending Balance	(442,947)	25,615	(442,947)	25,615
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,653	637	(46,024)	2,154
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI	1,653	637	(46,024)	2,154
Reclassification out of Accumulated Other Comprehensive Income | Net Unrealized (Loss) Gain on Interest Rate Swaps 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