Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Securities - Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities (Details)

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Note 4 - Securities - Amortized Cost and Fair Value of Available-for-sale and Held-to-maturity Securities (Details) - USD ($)
$ in Thousands
Mar. 31, 2024
Dec. 31, 2023
Available for sale, amortized cost $ 1,139,325 $ 969,090
Available for sale, gross unrealized gain 320 258
Available for sale, gross unrealized loss (65,716) (69,166)
Available for sale, fair value 1,073,929 900,183 [1]
Held to maturity, amortized cost 867,696 982,664 [1]
Held to maturity, gross unrealized gain 5 3
Held to maturity, gross unrealized loss (82,431) (75,475)
Held to maturity debt securities, fair value 785,270 907,191
US Treasury Securities [Member]    
Available for sale, amortized cost 494,156 340,556
Available for sale, gross unrealized gain 10 251
Available for sale, gross unrealized loss (197) 0
Available for sale, fair value 493,969 340,807
Held to maturity, amortized cost 393,932 508,985
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (25,065) (24,718)
Held to maturity debt securities, fair value 368,868 484,267
Collateralized Mortgage-Backed Securities [Member]    
Available for sale, amortized cost 281,343 241,458
Available for sale, gross unrealized gain 249 6
Available for sale, gross unrealized loss (26,677) (25,979)
Available for sale, fair value 254,915 215,485
Held to maturity, amortized cost 465,695 465,615
Held to maturity, gross unrealized gain 5 3
Held to maturity, gross unrealized loss (56,634) (50,025)
Held to maturity debt securities, fair value 409,066 415,593
US States and Political Subdivisions Debt Securities [Member]    
Available for sale, amortized cost 11,142 11,400
Available for sale, gross unrealized gain 1 1
Available for sale, gross unrealized loss (1,186) (1,178)
Available for sale, fair value 9,958 10,223
Held to maturity, amortized cost 8,069 8,063
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (733) (732)
Held to maturity debt securities, fair value 7,336 7,331
Corporate Debt Securities [Member]    
Available for sale, amortized cost 352,684 375,676
Available for sale, gross unrealized gain 60 0
Available for sale, gross unrealized loss (37,657) (42,009)
Available for sale, fair value $ 315,086 $ 333,667
[1] derived from audited financial statements.