Investment Securities - Fair Value of Investments with Sustained Gross Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	$ 56,640	$ 507,751
Available-for-sale, Less than 12 months, Unrealized Losses	(1,605)	(70,248)
Available-for-sale, 12 months or longer, Fair Value	1,092,621	677,083
Available-for-sale, 12 months or longer, Unrealized losses	(211,927)	(143,282)
Available-for-sale, Total Fair Value	1,149,261	1,184,834
Available-for-sale, Total Unrealized Losses	(213,532)	(213,530)
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	1,553	57,007
Available-for-sale, Less than 12 months, Unrealized Losses	(18)	(3,493)
Available-for-sale, 12 months or longer, Fair Value	213,600	163,520
Available-for-sale, 12 months or longer, Unrealized losses	(31,540)	(28,914)
Available-for-sale, Total Fair Value	215,153	220,527
Available-for-sale, Total Unrealized Losses	(31,558)	(32,407)
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	42,383	220,102
Available-for-sale, Less than 12 months, Unrealized Losses	(591)	(43,221)
Available-for-sale, 12 months or longer, Fair Value	230,437	45,419
Available-for-sale, 12 months or longer, Unrealized losses	(55,831)	(16,624)
Available-for-sale, Total Fair Value	272,820	265,521
Available-for-sale, Total Unrealized Losses	(56,422)	(59,845)
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	2,862	165,966
Available-for-sale, Less than 12 months, Unrealized Losses	(95)	(19,859)
Available-for-sale, 12 months or longer, Fair Value	590,760	461,446
Available-for-sale, 12 months or longer, Unrealized losses	(119,552)	(96,900)
Available-for-sale, Total Fair Value	593,622	627,412
Available-for-sale, Total Unrealized Losses	(119,647)	(116,759)
Other Securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Available-for-sale, Less than 12 months, Fair Value	9,842	64,676
Available-for-sale, Less than 12 months, Unrealized Losses	(901)	(3,675)
Available-for-sale, 12 months or longer, Fair Value	57,824	6,698
Available-for-sale, 12 months or longer, Unrealized losses	(5,004)	(844)
Available-for-sale, Total Fair Value	67,666	71,374
Available-for-sale, Total Unrealized Losses	$ (5,905)	$ (4,519)

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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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