Investment Securities - Securities Temporarily Impaired (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	$ 96,442	$ 251,182	$ 337,576
Unrealized Losses (Less than 12 months)	(7,156)	(23,126)	(61,255)
Fair Value (Estimated) (12 months or more)	453,732	310,159	223,562
Unrealized Losses (12 months or more)	(136,976)	(88,620)	(67,276)
Fair Value (Estimated)	550,174	561,341	561,138
Unrealized Losses	(144,132)	(111,746)	(128,531)
U.S. Treasury & Agency securities
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	11,842	4,804	7,364
Unrealized Losses (Less than 12 months)	(40)	(675)	(1,264)
Fair Value (Estimated) (12 months or more)	44,577	41,965	39,452
Unrealized Losses (12 months or more)	(19,555)	(16,680)	(16,043)
Fair Value (Estimated)	56,419	46,769	46,816
Unrealized Losses	(19,595)	(17,355)	(17,307)
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	18,017	73,509	109,041
Unrealized Losses (Less than 12 months)	(441)	(6,486)	(13,868)
Fair Value (Estimated) (12 months or more)	238,150	197,102	162,979
Unrealized Losses (12 months or more)	(63,825)	(47,353)	(41,957)
Fair Value (Estimated)	256,167	270,611	272,020
Unrealized Losses	(64,266)	(53,839)	(55,825)
State and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	66,583	149,517	197,145
Unrealized Losses (Less than 12 months)	(6,675)	(13,769)	(44,277)
Fair Value (Estimated) (12 months or more)	147,818	67,932	17,902
Unrealized Losses (12 months or more)	(49,769)	(24,247)	(9,005)
Fair Value (Estimated)	214,401	217,449	215,047
Unrealized Losses	(56,444)	(38,016)	(53,282)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	0	3,495	3,840
Unrealized Losses (Less than 12 months)	0	(53)	(32)
Fair Value (Estimated) (12 months or more)	1,510	0	0
Unrealized Losses (12 months or more)	(4)	0	0
Fair Value (Estimated)	1,510	3,495	3,840
Unrealized Losses	(4)	(53)	(32)
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Fair Value (Estimated) (Less than 12 months)	0	19,857	20,186
Unrealized Losses (Less than 12 months)	0	(2,143)	(1,814)
Fair Value (Estimated) (12 months or more)	21,677	3,160	3,229
Unrealized Losses (12 months or more)	(3,823)	(340)	(271)
Fair Value (Estimated)	21,677	23,017	23,415
Unrealized Losses	$ (3,823)	$ (2,483)	$ (2,085)

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