Securities, Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Securities [Abstract]
Percentage of total investment with unrealized losses	98.90%	97.40%
Available-for-sale, amortized cost [Abstract]
Less than 12 months	$ 46,468	$ 416,778
12 months or more	1,265,661	981,280
Total	1,312,129	1,398,058
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(3,078)	(21,324)
12 months or more	(185,319)	(153,300)
Total	(188,397)	(174,624)
Available-for-sale, fair value [Abstract]
Less than 12 months	43,390	395,454
12 months or more	1,080,342	827,980
Total	1,123,732	1,223,434
U.S. Treasury and Government Agencies [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	4,781	144,305
12 months or more	370,697	249,424
Total	375,478	393,729
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(6)	(6,953)
12 months or more	(35,802)	(29,906)
Total	(35,808)	(36,859)
Available-for-sale, fair value [Abstract]
Less than 12 months	4,775	137,352
12 months or more	334,895	219,518
Total	339,670	356,870
State and Political Subdivisions [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	25,808	94,277
12 months or more	287,629	225,019
Total	313,437	319,296
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(2,565)	(6,257)
12 months or more	(66,825)	(55,419)
Total	(69,390)	(61,676)
Available-for-sale, fair value [Abstract]
Less than 12 months	23,243	88,020
12 months or more	220,804	169,600
Total	244,047	257,620
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	15,879	139,314
12 months or more	518,517	454,357
Total	534,396	593,671
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(507)	(6,883)
12 months or more	(81,637)	(66,950)
Total	(82,144)	(73,833)
Available-for-sale, fair value [Abstract]
Less than 12 months	15,372	132,431
12 months or more	436,880	387,407
Total	452,252	519,838
Asset-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	0	38,882
12 months or more	88,818	52,480
Total	88,818	91,362
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	0	(1,231)
12 months or more	(1,055)	(1,025)
Total	(1,055)	(2,256)
Available-for-sale, fair value [Abstract]
Less than 12 months	0	37,651
12 months or more	87,763	51,455
Total	$ 87,763	$ 89,106