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
Jun. 30, 2023
Dec. 31, 2022
Available for sale, amortized cost $ 1,075,006 $ 707,376
Available for sale, gross unrealized gain 50 6
Available for sale, gross unrealized loss (84,135) (62,567)
Available for sale, fair value 990,921 644,815 [1]
Held to maturity, amortized cost 1,057,306 1,034,121 [1]
Held to maturity, gross unrealized gain 1 7
Held to maturity, gross unrealized loss (93,464) (98,175)
Held to maturity debt securities, fair value 963,843 935,953
US Treasury Securities [Member]    
Available for sale, amortized cost 414,470 3,002
Available for sale, gross unrealized gain 47 0
Available for sale, gross unrealized loss (63) (33)
Available for sale, fair value 414,454 2,969
Held to maturity, amortized cost 557,084 507,151
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (34,258) (36,197)
Held to maturity debt securities, fair value 522,826 470,954
US Government Agencies Debt Securities [Member]    
Available for sale, amortized cost 4 9
Available for sale, gross unrealized gain 0 0
Available for sale, gross unrealized loss 0 0
Available for sale, fair value 4 9
Collateralized Mortgage-Backed Securities [Member]    
Available for sale, amortized cost 261,450 282,480
Available for sale, gross unrealized gain 2 5
Available for sale, gross unrealized loss (31,510) (32,782)
Available for sale, fair value 229,942 249,703
Held to maturity, amortized cost 492,170 518,929
Held to maturity, gross unrealized gain 1 7
Held to maturity, gross unrealized loss (58,302) (60,960)
Held to maturity debt securities, fair value 433,869 457,976
US States and Political Subdivisions Debt Securities [Member]    
Available for sale, amortized cost 13,409 15,205
Available for sale, gross unrealized gain 1 1
Available for sale, gross unrealized loss (1,447) (1,597)
Available for sale, fair value 11,963 13,609
Held to maturity, amortized cost 8,052 8,041
Held to maturity, gross unrealized gain 0 0
Held to maturity, gross unrealized loss (904) (1,018)
Held to maturity debt securities, fair value 7,148 7,023
Corporate Debt Securities [Member]    
Available for sale, amortized cost 385,673 406,680
Available for sale, gross unrealized gain 0 0
Available for sale, gross unrealized loss (51,115) (28,155)
Available for sale, fair value $ 334,558 $ 378,525
[1] derived from audited financial statements.