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Securities - Amortized Cost and Fair Value (Details) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 USD ($) item | Dec. 31, 2021 USD ($)
Securities Available-for-Sale |  |
Amortized Cost | $ 1,662,819 | $ 1,678,160
Gross Unrealized Gains | 370 | 20,587
Gross Unrealized Losses | (123,830) | (5,115)
Securities available-for-sale | 1,539,359 | 1,693,632
Accrued interest receivable | 6,800 | 4,300
FHLB and FRB Stock |  |
FHLBC stock | 5,600 | 7,100
FRBC stock | 14,900 | 6,200
Securities pledged to secure deposits and for other purposes | 547,800 | 501,300
Other disclosures |  |
Securities available-for-sale | $ 1,539,359 | 1,693,632
Number of securities issued from originators | 0 |
Number of originators | item | 1 |
Minimum percentage of securities investment | 10.00% |
US government and agencies debt securities, percentage of guarantee | 100.00% |
US government and agencies debt securities, threshold percentage of guarantee for allowance of credit loss | 100.00% |
Reimbursement requests greater than 5 % |  |
Other disclosures |  |
Percentage of outstanding principal amount of loans guaranteed by US Department of Education | 85 |
Percent of insured loan | 5 |
Reimbursement requests greater than 9 % |  |
Other disclosures |  |
Percentage of outstanding principal amount of loans guaranteed by US Department of Education | 75 |
Percent of insured loan | 9 |
U.S. Treasury |  |
Securities Available-for-Sale |  |
Amortized Cost | $ 224,054 | 202,251
Gross Unrealized Gains |  | 125
Gross Unrealized Losses | (11,925) | (37)
Securities available-for-sale | 212,129 | 202,339
Other disclosures |  |
Securities available-for-sale | 212,129 | 202,339
U.S. government agencies |  |
Securities Available-for-Sale |  |
Amortized Cost | 61,178 | 62,587
Gross Unrealized Losses | (5,130) | (699)
Securities available-for-sale | 56,048 | 61,888
Other disclosures |  |
Securities available-for-sale | 56,048 | 61,888
U.S. government agencies mortgage-backed |  |
Securities Available-for-Sale |  |
Amortized Cost | 140,588 | 172,016
Gross Unrealized Gains |  | 856
Gross Unrealized Losses | (15,598) | (570)
Securities available-for-sale | 124,990 | 172,302
Other disclosures |  |
Securities available-for-sale | 124,990 | 172,302
States and political subdivisions |  |
Securities Available-for-Sale |  |
Amortized Cost | 239,999 | 241,937
Gross Unrealized Gains | 363 | 16,344
Gross Unrealized Losses | (14,234) | (672)
Securities available-for-sale | 226,128 | 257,609
Other disclosures |  |
Securities available-for-sale | 226,128 | 257,609
Corporate bonds |  |
Securities Available-for-Sale |  |
Amortized Cost | 10,000 | 10,000
Gross Unrealized Losses | (378) | (113)
Securities available-for-sale | 9,622 | 9,887
Other disclosures |  |
Securities available-for-sale | 9,622 | 9,887
Collateralized mortgage obligations |  |
Securities Available-for-Sale |  |
Amortized Cost | 596,336 | 673,238
Gross Unrealized Gains | 1 | 2,014
Gross Unrealized Losses | (62,569) | (2,285)
Securities available-for-sale | 533,768 | 672,967
Other disclosures |  |
Securities available-for-sale | 533,768 | 672,967
Asset-backed Securities |  |
Securities Available-for-Sale |  |
Amortized Cost | 210,388 | 236,293
Gross Unrealized Gains | 6 | 1,245
Gross Unrealized Losses | (8,466) | (661)
Securities available-for-sale | 201,928 | 236,877
Other disclosures |  |
Securities available-for-sale | 201,928 | 236,877
FFEL |  |
Securities Available-for-Sale |  |
Securities available-for-sale | 160,800 |
Other disclosures |  |
Securities available-for-sale | $ 160,800 |
Percentage of outstanding principal amount of loans guaranteed by US Department of Education | 97 |
Collateralized loan obligations. |  |
Securities Available-for-Sale |  |
Amortized Cost | $ 180,276 | 79,838
Gross Unrealized Gains |  | 3
Gross Unrealized Losses | (5,530) | (78)
Securities available-for-sale | 174,746 | 79,763
Other disclosures |  |
Securities available-for-sale | $ 174,746 | $ 79,763
Loan receivables | GCO Education Loan Funding Corp | Customer Concentration Risk |  |
Other disclosures |  |
Percentage of concentration risk | 1.00% |
Minimum |  |
Other disclosures |  |
Debt securities, available-for-sale, allowance for credit loss, percent of market value loss | 5.00% |
Debt securities, available-for-sale, allowance for credit loss, market value loss | $ 200,000 |

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