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Investment Securities (Tables) | 9 Months Ended
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Sep. 30, 2023
Investment Securities |
Schedule of amortized cost of investment securities to estimated fair values | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | September 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 | ​ | $ | 2,679 | ​ | $ | 9 | ​ | $ | (23) | ​ | $ | — | ​ | $ | 2,665
Mortgage backed securities | ​ |  |  | ​ |  | ​ | ​ |  | ​ | ​ | ​ | ​ | ​ |  | ​
Residential agency | ​ |  | 656,845 | ​ |  | — | ​ |  | (135,222) | ​ | ​ | — | ​ |  | 521,623
Commercial | ​ |  | 66,980 | ​ |  | — | ​ |  | (8,295) | ​ | ​ | — | ​ |  | 58,685
Asset backed securities | ​ |  | 27 | ​ |  | — | ​ |  | — | ​ | ​ | — | ​ |  | 27
Corporate bonds | ​ |  | 69,495 | ​ |  | — | ​ |  | (12,494) | ​ | ​ | — | ​ |  | 57,001
Total available-for-sale investment securities | ​ | ​ | 796,026 | ​ | ​ | 9 | ​ | ​ | (156,034) | ​ | ​ | — | ​ | ​ | 640,001
Held-to-maturity | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Obligations of state and political agencies | ​ | ​ | 130,088 | ​ |  | — | ​ |  | (18,651) | ​ | ​ | 115 | ​ |  | 111,437
Mortgage backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | 173,398 | ​ |  | — | ​ |  | (36,596) | ​ | ​ | 103 | ​ |  | 136,802
Total held-to-maturity investment securities | ​ | ​ | 303,486 | ​ | ​ | — | ​ | ​ | (55,247) | ​ | ​ | 218 | ​ | ​ | 248,239
Total investment securities | ​ | $ | 1,099,512 | ​ | $ | 9 | ​ | $ | (211,281) | ​ | $ | 218 | ​ | $ | 888,240
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | 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 | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | September 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 | ​ | $ | — | ​ | $ | — | ​ | $ | (23) | ​ | $ | 389 | ​ | $ | (23) | ​ | $ | 389
Mortgage backed securities | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Residential agency | ​ |  | (9) | ​ |  | 577 | ​ |  | (135,213) | ​ |  | 484,451 | ​ |  | (135,222) | ​ |  | 485,028
Commercial | ​ |  | — | ​ |  | — | ​ |  | (8,295) | ​ |  | 58,684 | ​ |  | (8,295) | ​ |  | 58,684
Asset backed securities | ​ |  | — | ​ |  | 7 | ​ |  | — | ​ |  | 19 | ​ |  | — | ​ |  | 26
Corporate bonds | ​ |  | — | ​ |  | — | ​ |  | (12,494) | ​ |  | 57,001 | ​ |  | (12,494) | ​ |  | 57,001
Total available-for-sale investment securities | ​ | $ | (9) | ​ | $ | 584 | ​ | $ | (156,025) | ​ | $ | 600,544 | ​ | $ | (156,034) | ​ | $ | 601,128
​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | 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 | ​ | $ | 5,981 | ​ | $ | 5,875 | ​ | $ | — | ​ | $ | —
Due after one year through five years | ​ |  | 51,009 | ​ |  | 45,878 | ​ |  | 17,119 | ​ |  | 15,706
Due after five years through ten years | ​ |  | 60,325 | ​ |  | 49,427 | ​ |  | 80,670 | ​ |  | 66,779
Due after 10 years | ​ |  | 12,773 | ​ |  | 10,257 | ​ |  | 41,392 | ​ |  | 35,893
​ | ​ | ​ | 130,088 | ​ | ​ | 111,437 | ​ | ​ | 139,181 | ​ | ​ | 118,378
Mortgage-backed securities | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Residential agency | ​ | ​ | 173,398 | ​ | ​ | 136,802 | ​ | ​ | 656,845 | ​ | ​ | 521,623
Total investment securities | ​ | $ | 303,486 | ​ | $ | 248,239 | ​ | $ | 796,026 | ​ | $ | 640,001
Schedule of proceeds from the call of held-to-maturity investment securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three months ended | ​ | Nine months ended
​ | ​ | September 30, | ​ | September 30,
(dollars in thousands) |  | 2023 |  | 2022 |  | 2023 |  | 2022
Proceeds | ​ | $ | 116 | ​ | $ | 101 | ​ | $ | 242 | ​ | $ | 827
Realized gains | ​ |  | — | ​ |  | — | ​ |  | — | ​ |  | —
Realized losses | ​ |  | — | ​ |  | — | ​ |  | — | ​ |  | —
​
Schedule of federal home loan bank | ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | September 30, | ​ | December 31,
(dollars in thousands) |  | 2023 |  | 2022
Federal Reserve | ​ | $ | 4,623 | ​ | $ | 4,595
FHLB | ​ |  | 25,316 | ​ |  | 19,362

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