Accumulated Other Comprehensive (Loss) Income - Changes in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Equity [Abstract]
Unrealized loss on securities, before tax amount	$ (40,361)	$ (114,312)	$ 1,838	$ (313,379)
Unrealized loss on securities, tax effect	9,142	25,960	(416)	71,168
Unrealized loss on securities, net of tax amount	(31,219)	(88,352)	1,422	(242,211)
Reclassification adjustment for securities gain included in net income, before tax amount	(4)	8	18	27
Reclassification adjustment for securities gain included in net income, tax effect	1	(2)	(4)	(6)
Reclassification adjustment for securities gain included in net income, net of tax amount	(3)	6	14	21
Amortization of net unrealized losses on AFS securities transferred to HTM. before-tax amount	1,941	(62,250)	3,851	(61,686)
Amortization of net unrealized losses on AFS securities transferred to HTM, tax	(440)	14,137	(872)	14,009
Amortization of net unrealized losses on AFS securities transferred to HTM, net of tax amount	1,501	(48,113)	2,979	(47,677)
Net unrealized loss on interest rate swaps used in cash flow hedges, before-tax amount	(7,251)	(11,100)	5,284	(51,663)
Net unrealized loss on interest rate swaps used in cash flow hedges, before-tax amount	1,665	2,514	(17,690)	11,701
Amount of Gain (Loss) Recognized in OCI on Derivative	(5,586)	(8,586)	(12,406)	(39,962)
Net unrealized losses on interest rate swaps used in cash flow hedges, before-tax amount	7,032	(434)	14,189	(2,382)
Net unrealized losses on interest rate swaps used in cash flow hedges, tax	(22)	99	(36)	540
Net unrealized losses on interest rate swaps used in cash flow hedges, net of tax amount	7,010	(335)	14,153	(1,842)
Amortization of net unrecognized pension and postretirement items, before tax amount	4	33	36	65
Amortization of net unrecognized pension and postretirement items, tax effect	(1)	(8)	(8)	(15)
Amortization of net unrecognized pension and postretirement items, net of tax amount	3	25	28	50
Total Other Comprehensive Income, Before Tax Amount	(38,639)	(188,055)	25,216	(429,018)
Total Other Comprehensive Income, Tax Effect	10,345	42,700	(19,026)	97,397
Other Comprehensive Income (Loss)	$ (28,294)	$ (145,355)	$ 6,190	$ (331,621)