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Investment Securities (Tables) | 6 Months Ended
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Jun. 30, 2023
Investment Securities |
Schedule of amortized cost of investment securities to estimated fair values | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30, 2023
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | Allowance for | ​ | Fair
(dollars in thousands) |  | Cost | ​ | Gains | ​ | Losses | ​ | Credit Losses |  | Value
Available-for-sale | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. Treasury and agencies | ​ | $ | 2,915 | ​ | $ | 11 | ​ | $ | (20) | ​ | $ | — | ​ | $ | 2,906
Mortgage backed securities | ​ |  |  | ​ |  | ​ | ​ |  | ​ | ​ | ​ | ​ | ​ |  | ​
Residential agency | ​ |  | 673,586 | ​ |  | 1 | ​ |  | (115,131) | ​ | ​ | — | ​ |  | 558,456
Commercial | ​ |  | 68,379 | ​ |  | — | ​ |  | (7,470) | ​ | ​ | — | ​ |  | 60,909
Asset backed securities | ​ |  | 28 | ​ |  | — | ​ |  | — | ​ | ​ | — | ​ |  | 28
Corporate bonds | ​ |  | 69,497 | ​ |  | — | ​ |  | (14,342) | ​ | ​ | — | ​ |  | 55,155
Total available-for-sale investment securities | ​ | ​ | 814,405 | ​ | ​ | 12 | ​ | ​ | (136,963) | ​ | ​ | — | ​ | ​ | 677,454
Held-to-maturity | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Obligations of state and political agencies | ​ | ​ | 131,016 | ​ |  | — | ​ |  | (15,447) | ​ | ​ | 115 | ​ |  | 115,569
Mortgage backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | 177,618 | ​ |  | — | ​ |  | (32,477) | ​ | ​ | 103 | ​ |  | 145,141
Total held-to-maturity investment securities | ​ | ​ | 308,634 | ​ | ​ | — | ​ | ​ | (47,924) | ​ | ​ | 218 | ​ | ​ | 260,710
Total investment securities | ​ | $ | 1,123,039 | ​ | $ | 12 | ​ | $ | (184,887) | ​ | $ | 218 | ​ | $ | 938,164
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2022
​ | ​ | Amortized | ​ | Unrealized | ​ | Unrealized | ​ | Allowance for | ​ | Fair
(dollars in thousands) |  | Cost | ​ | Gains | ​ | Losses | ​ | Credit Losses |  | Value
Available-for-sale | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. Treasury and agencies | ​ | $ | 3,518 | ​ | $ | 19 | ​ | $ | (17) | ​ | ​ | N/A | ​ | $ | 3,520
Mortgage backed securities | ​ |  |  | ​ |  | ​ | ​ |  | ​ | ​ | ​ | ​ | ​ |  |
Residential agency | ​ |  | 705,845 | ​ |  | 2 | ​ |  | (118,168) | ​ | ​ | N/A | ​ |  | 587,679
Commercial | ​ |  | 70,669 | ​ |  | — | ​ |  | (7,111) | ​ | ​ | N/A | ​ |  | 63,558
Asset backed securities | ​ |  | 34 | ​ |  | — | ​ |  | — | ​ | ​ | N/A | ​ |  | 34
Corporate bonds | ​ |  | 69,501 | ​ |  | — | ​ |  | (6,968) | ​ | ​ | N/A | ​ |  | 62,533
Total available-for-sale investment securities | ​ | ​ | 849,567 | ​ | ​ | 21 | ​ | ​ | (132,264) | ​ | ​ | N/A | ​ | ​ | 717,324
Held-to-maturity | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Obligations of state and political agencies | ​ | ​ | 137,787 | ​ |  | — | ​ |  | (17,736) | ​ | ​ | N/A | ​ | ​ | 120,051
Mortgage backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | 184,115 | ​ |  | — | ​ |  | (33,254) | ​ | ​ | N/A | ​ | ​ | 150,861
Total held-to-maturity investment securities | ​ | ​ | 321,902 | ​ | ​ | — | ​ | ​ | (50,990) | ​ | ​ | N/A | ​ | ​ | 270,912
Total investment securities | ​ | $ | 1,171,469 | ​ | $ | 21 | ​ | $ | (183,254) | ​ | ​ | N/A | ​ | $ | 988,236
Schedule of investment securities with gross unrealized losses | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30, 2023
​ | ​ | Less than 12 Months | ​ | Over 12 Months | ​ | Total
​ | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair
(dollars in thousands) |  | Losses |  | Value |  | Losses |  | Value |  | Losses |  | Value
Available-for-sale | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. Treasury and agencies | ​ | $ | (20) | ​ | $ | 420 | ​ | $ | — | ​ | $ | — | ​ | $ | (20) | ​ | $ | 420
Mortgage backed securities | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Residential agency | ​ |  | (76) | ​ |  | 2,148 | ​ |  | (115,055) | ​ |  | 556,258 | ​ |  | (115,131) | ​ |  | 558,406
Commercial | ​ |  | (32) | ​ |  | 570 | ​ |  | (7,438) | ​ |  | 60,339 | ​ |  | (7,470) | ​ |  | 60,909
Asset backed securities | ​ |  | — | ​ |  | 27 | ​ |  | — | ​ |  | 1 | ​ |  | — | ​ |  | 28
Corporate bonds | ​ |  | (867) | ​ |  | 7,109 | ​ |  | (13,475) | ​ |  | 48,046 | ​ |  | (14,342) | ​ |  | 55,155
Total available-for-sale investment securities | ​ | $ | (995) | ​ | $ | 10,274 | ​ | $ | (135,968) | ​ | $ | 664,644 | ​ | $ | (136,963) | ​ | $ | 674,918
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, 2022
​ | ​ | Less than 12 Months | ​ | Over 12 Months | ​ | Total
​ | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair | ​ | Unrealized | ​ | Fair
(dollars in thousands) |  | Losses |  | Value |  | Losses |  | Value |  | Losses |  | Value
Available-for-sale | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
U.S. Treasury and agencies | ​ | $ | (17) | ​ | $ | 509 | ​ | $ | — | ​ | $ | — | ​ | $ | (17) | ​ | $ | 509
Mortgage backed securities | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Residential agency | ​ |  | (10,457) | ​ |  | 79,693 | ​ |  | (107,711) | ​ |  | 507,418 | ​ |  | (118,168) | ​ |  | 587,111
Commercial | ​ |  | (4,835) | ​ |  | 50,437 | ​ |  | (2,276) | ​ |  | 13,120 | ​ |  | (7,111) | ​ |  | 63,557
Asset backed securities | ​ |  | — | ​ |  | 32 | ​ |  | — | ​ |  | 2 | ​ |  | — | ​ |  | 34
Corporate bonds | ​ |  | (4,452) | ​ |  | 48,048 | ​ |  | (2,516) | ​ |  | 14,484 | ​ |  | (6,968) | ​ |  | 62,532
Total available-for-sale investment securities | ​ | ​ | (19,761) | ​ | ​ | 178,719 | ​ | ​ | (112,503) | ​ | ​ | 535,024 | ​ | ​ | (132,264) | ​ | ​ | 713,743
Held-to-maturity | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Obligations of state and political agencies | ​ | ​ | (3,336) | ​ | ​ | 18,788 | ​ | ​ | (14,400) | ​ | ​ | 98,762 | ​ | ​ | (17,736) | ​ | ​ | 117,550
Mortgage backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | — | ​ | ​ | — | ​ | ​ | (33,254) | ​ | ​ | 150,861 | ​ | ​ | (33,254) | ​ | ​ | 150,861
Total held-to-maturity investment securities | ​ | ​ | (3,336) | ​ | ​ | 18,788 | ​ | ​ | (47,654) | ​ | ​ | 249,623 | ​ | ​ | (50,990) | ​ | ​ | 268,411
Total investment securities | ​ | $ | (23,097) | ​ | $ | 197,507 | ​ | $ | (160,157) | ​ | $ | 784,647 | ​ | $ | (183,254) | ​ | $ | 982,154
Schedule of contractual maturity of amortized cost and estimated fair value | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Held-to-maturity | ​ | Available-for-sale
​ | ​ | Carrying | ​ | Fair | ​ | Amortized | ​ | Fair
(dollars in thousands) |  | Value | ​ | Value | ​ | Cost |  | Value
Due within one year or less | ​ | $ | 6,098 | ​ | $ | 5,946 | ​ | $ | — | ​ | $ | —
Due after one year through five years | ​ |  | 44,352 | ​ |  | 40,512 | ​ |  | 17,461 | ​ |  | 16,096
Due after five years through ten years | ​ |  | 67,751 | ​ |  | 58,000 | ​ |  | 78,734 | ​ |  | 63,524
Due after 10 years | ​ |  | 12,815 | ​ |  | 11,111 | ​ |  | 44,624 | ​ |  | 39,378
​ | ​ | ​ | 131,016 | ​ | ​ | 115,569 | ​ | ​ | 140,819 | ​ | ​ | 118,998
Mortgage-backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | 177,618 | ​ | ​ | 145,141 | ​ | ​ | 673,586 | ​ | ​ | 558,456
Total investment securities | ​ | $ | 308,634 | ​ | $ | 260,710 | ​ | $ | 814,405 | ​ | $ | 677,454
Schedule of proceeds from the call of held-to-maturity investment securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended | ​ | Six months ended
​ | ​ | June 30, | ​ | June 30,
(dollars in thousands) |  | 2023 |  | 2022 |  | 2023 |  | 2022
Proceeds | ​ | $ | — | ​ | $ | 211 | ​ | $ | 126 | ​ | $ | 726
Realized gains | ​ |  | — | ​ |  | — | ​ |  | — | ​ |  | —
Realized losses | ​ |  | — | ​ |  | — | ​ |  | — | ​ |  | —
​
Schedule of federal home loan bank | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30, | ​ | December 31,
(dollars in thousands) |  | 2023 |  | 2022
Federal Reserve | ​ | $ | 4,623 | ​ | $ | 4,595
FHLB | ​ |  | 24,382 | ​ |  | 19,362

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