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
Sep. 30, 2023
Dec. 31, 2022
Available for sale, amortized cost $ 920,243 $ 707,376
Available for sale, gross unrealized gain 8 6
Available for sale, gross unrealized loss (85,449) (62,567)
Available for sale, fair value 834,802 644,815 [1]
Held to maturity, amortized cost 1,043,899 1,034,121 [1]
Held to maturity, gross unrealized gain 0 7
Held to maturity, gross unrealized loss (110,893) (98,175)
Held to maturity debt securities, fair value 933,006 935,953
US Treasury Securities [Member]    
Available for sale, amortized cost 280,807 3,002
Available for sale, gross unrealized gain 7 0
Available for sale, gross unrealized loss (96) (33)
Available for sale, fair value 280,718 2,969
Held to maturity, amortized cost 558,196 507,151
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (35,014) (36,197)
Held to maturity debt securities, fair value 523,182 470,954
Collateralized Mortgage-Backed Securities [Member]    
Available for sale, amortized cost 251,001 282,480
Available for sale, gross unrealized gain 0 5
Available for sale, gross unrealized loss (35,760) (32,782)
Available for sale, fair value 215,241 249,703
Held to maturity, amortized cost 477,646 518,929
Held to maturity, gross unrealized gain 0 7
Held to maturity, gross unrealized loss (74,928) (60,960)
Held to maturity debt securities, fair value 402,718 457,976
US States and Political Subdivisions Debt Securities [Member]    
Available for sale, amortized cost 12,762 15,205
Available for sale, gross unrealized gain 1 1
Available for sale, gross unrealized loss (1,570) (1,597)
Available for sale, fair value 11,193 13,609
Held to maturity, amortized cost 8,057 8,041
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (951) (1,018)
Held to maturity debt securities, fair value 7,106 7,023
Corporate Debt Securities [Member]    
Available for sale, amortized cost 375,673 406,680
Available for sale, gross unrealized gain 0 0
Available for sale, gross unrealized loss (48,023) (28,155)
Available for sale, fair value 327,650 $ 378,525
US Government Agencies Debt Securities [Member]    
Available for sale, amortized cost 9  
Available for sale, gross unrealized gain 0  
Available for sale, gross unrealized loss 0  
Available for sale, fair value $ 9  
[1] derived from audited financial statements.