Investment Securities - Fair Value of Investments with Sustained Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	$ 39,707	$ 34,698
Available-for-sale, Less than 12 months, Unrealized Losses	(869)	(843)
Available-for-sale, 12 months or longer, Fair Value	1,057,538	1,075,835
Available-for-sale, 12 months or longer, Unrealized losses	(203,245)	(192,616)
Available-for-sale, Total Fair Value	1,097,245	1,110,533
Available-for-sale, Total Unrealized Losses	(204,114)	(193,459)
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	1,295	1,288
Available-for-sale, Less than 12 months, Unrealized Losses	0	(4)
Available-for-sale, 12 months or longer, Fair Value	206,025	210,069
Available-for-sale, 12 months or longer, Unrealized losses	(27,220)	(26,215)
Available-for-sale, Total Fair Value	207,320	211,357
Available-for-sale, Total Unrealized Losses	(27,220)	(26,219)
Obligations of States and Political Subdivisions
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	27,302	22,281
Available-for-sale, Less than 12 months, Unrealized Losses	(324)	(333)
Available-for-sale, 12 months or longer, Fair Value	248,168	241,630
Available-for-sale, 12 months or longer, Unrealized losses	(52,540)	(49,038)
Available-for-sale, Total Fair Value	275,470	263,911
Available-for-sale, Total Unrealized Losses	(52,864)	(49,371)
Mortgage-backed Securities: GSE Residential
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	5,773	5,818
Available-for-sale, Less than 12 months, Unrealized Losses	(132)	(67)
Available-for-sale, 12 months or longer, Fair Value	545,899	566,197
Available-for-sale, 12 months or longer, Unrealized losses	(119,639)	(113,007)
Available-for-sale, Total Fair Value	551,672	572,015
Available-for-sale, Total Unrealized Losses	(119,771)	(113,074)
Other Securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	5,337	5,311
Available-for-sale, Less than 12 months, Unrealized Losses	(413)	(439)
Available-for-sale, 12 months or longer, Fair Value	57,446	57,939
Available-for-sale, 12 months or longer, Unrealized losses	(3,846)	(4,356)
Available-for-sale, Total Fair Value	62,783	63,250
Available-for-sale, Total Unrealized Losses	$ (4,259)	$ (4,795)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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