Investment Securities - Unrealized Losses and Estimated Fair Value of Investment Securities Available for Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	$ 267,817	$ 77,407
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(3,709)	(753)
Fair Value of Available-for-Sale Securities, 12 Months or More	2,140,713	2,303,038
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(223,202)	(222,629)
Fair Value of Available-for-Sale Securities, Total	2,408,530	2,380,445
Unrealized Losses of Available-for-Sale Securities, Total	(226,911)	(223,382)
Held-to-maturity:
Fair Value of Held-to-Maturity Securities, Less Than 12 Months	82,972	35,900
Unrealized Losses of Held-to-Maturity Securities, Less Than 12 Months	(1,619)	(231)
Fair Value of Held-to-Maturity Securities, 12 Months or More	1,045,150	1,090,389
Unrealized Losses of Held-to-Maturity Securities, 12 Months or More	(104,503)	(98,450)
Fair Value of Held-to-Maturity Securities, Total	1,128,122	1,126,289
Unrealized Losses of Held-to-Maturity Securities	(106,122)	(98,681)
U.S. government-sponsored enterprises
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	4,591	7,152
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(15)	(32)
Fair Value of Available-for-Sale Securities, 12 Months or More	140,606	165,091
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(7,222)	(7,075)
Fair Value of Available-for-Sale Securities, Total	145,197	172,243
Unrealized Losses of Available-for-Sale Securities, Total	(7,237)	(7,107)
Held-to-maturity:
Fair Value of Held-to-Maturity Securities, Less Than 12 Months	14,835	0
Unrealized Losses of Held-to-Maturity Securities, Less Than 12 Months	(165)	0
Fair Value of Held-to-Maturity Securities, 12 Months or More	27,217	42,451
Unrealized Losses of Held-to-Maturity Securities, 12 Months or More	(1,767)	(1,391)
Fair Value of Held-to-Maturity Securities, Total	42,052	42,451
Unrealized Losses of Held-to-Maturity Securities	(1,932)	(1,391)
U.S. government-sponsored mortgage-backed securities
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	81,372	26,462
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(1,263)	(136)
Fair Value of Available-for-Sale Securities, 12 Months or More	1,018,954	1,087,888
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(143,020)	(133,863)
Fair Value of Available-for-Sale Securities, Total	1,100,326	1,114,350
Unrealized Losses of Available-for-Sale Securities, Total	(144,283)	(133,999)
Held-to-maturity:
Fair Value of Held-to-Maturity Securities, Less Than 12 Months	42,013	16,763
Unrealized Losses of Held-to-Maturity Securities, Less Than 12 Months	(765)	(88)
Fair Value of Held-to-Maturity Securities, 12 Months or More	52,115	64,000
Unrealized Losses of Held-to-Maturity Securities, 12 Months or More	(3,987)	(3,170)
Fair Value of Held-to-Maturity Securities, Total	94,128	80,763
Unrealized Losses of Held-to-Maturity Securities	(4,752)	(3,258)
Private mortgage-backed securities
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	29,096	0
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(418)	0
Fair Value of Available-for-Sale Securities, 12 Months or More	130,408	135,255
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(8,276)	(6,984)
Fair Value of Available-for-Sale Securities, Total	159,504	135,255
Unrealized Losses of Available-for-Sale Securities, Total	(8,694)	(6,984)
Non-government-sponsored asset backed securities
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	20,472	22,987
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(130)	(13)
Fair Value of Available-for-Sale Securities, 12 Months or More	26,350	44,666
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(1,006)	(914)
Fair Value of Available-for-Sale Securities, Total	46,822	67,653
Unrealized Losses of Available-for-Sale Securities, Total	(1,136)	(927)
State and political subdivisions
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	63,734	15,301
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(1,058)	(505)
Fair Value of Available-for-Sale Securities, 12 Months or More	707,971	744,922
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(56,399)	(64,898)
Fair Value of Available-for-Sale Securities, Total	771,705	760,223
Unrealized Losses of Available-for-Sale Securities, Total	(57,457)	(65,403)
Held-to-maturity:
Fair Value of Held-to-Maturity Securities, Less Than 12 Months	26,124	19,137
Unrealized Losses of Held-to-Maturity Securities, Less Than 12 Months	(689)	(143)
Fair Value of Held-to-Maturity Securities, 12 Months or More	965,818	983,938
Unrealized Losses of Held-to-Maturity Securities, 12 Months or More	(98,749)	(93,889)
Fair Value of Held-to-Maturity Securities, Total	991,942	1,003,075
Unrealized Losses of Held-to-Maturity Securities	(99,438)	(94,032)
Other securities
Available-for-sale:
Fair Value of Available-for-Sale Securities, Less Than 12 Months	68,552	5,505
Unrealized Losses of Available-for-Sale Securities, Less Than 12 Months	(825)	(67)
Fair Value of Available-for-Sale Securities, 12 Months or More	116,424	125,216
Unrealized Losses of Available-for-Sale Securities, 12 Months or More	(7,279)	(8,895)
Fair Value of Available-for-Sale Securities, Total	184,976	130,721
Unrealized Losses of Available-for-Sale Securities, Total	$ (8,104)	$ (8,962)

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