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Investment Securities, Equity Securities with Readily Determinable Fair Values and Other Investments (Contractual Maturities and Estimated Fair Values) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Amortized Cost |  |  |  |  |
Due in one year or less, held-to-maturity debt securities amortized cost | $ 2,075,000 |  | $ 2,075,000 |  |
Due after one year through five years, held-to-maturity debt securities amortized cost | 1,325,000 |  | 1,325,000 |  |
Amortized cost, held-to-maturity debt securities | 3,400,000 |  | 3,400,000 |  | $ 3,400,000
Fair Value |  |  |  |  |
Due in one year or less, held-to-maturity debt securities, Estimated fair value | 2,075,000 |  | 2,075,000 |  |
Due after one year through five years, held-to-maturity debt securities, Estimated fair value | 1,325,000 |  | 1,325,000 |  |
Estimated fair value | 3,400,000 |  | 3,400,000 |  | 3,400,000
Available-for-sale debt securities amortized cost disclosures |  |  |  |  |
Due after five years through ten years, available-for-sale debt securities amortized cost | 440,000 |  | 440,000 |  |
Due after ten years, available-for-sale debt securities amortized cost | 160,678,000 |  | 160,678,000 |  |
Residential mortgage-backed securities, amortized cost | 5,227,139,000 |  | 5,227,139,000 |  |
Amortized cost, Available-for-sale securities | 5,388,257,000 |  | 5,388,257,000 |  | 5,018,996,000
Available for sale debt securities, Estimated Fair Value Disclosures |  |  |  |  |
Due after five years through ten years, available-for-sale debt securities, Estimated Fair Value | 431,000 |  | 431,000 |  |
Due after ten years, available-for-sale debt securities, Estimated Fair Value | 145,907,000 |  | 145,907,000 |  |
Residential mortgage-backed securities, Estimated Fair Value | 4,545,600,000 |  | 4,545,600,000 |  |
Estimated fair value, Available for sale securities | 4,691,938,000 |  | 4,691,938,000 |  | $ 4,417,796,000
Available for sale debt securities, Estimated Fair Value Disclosures |  |  |  |  |
Proceeds from sales and calls of available for sale securities | 1,595,000 | $ 800,000 | 2,045,000 | $ 800,000 |
Proceeds from sales of mortgage-backed securities | 0 | 0 | 0 | 0 |
Gross gains realized on sales | 0 | 0 | 0 | 0 |
Gross losses realized on sales | 3 | $ 0 | 3 | $ 0 |
Collateral Pledged |  |  |  |  |
Available-for-sale debt securities amortized cost disclosures |  |  |  |  |
Amortized cost, Available-for-sale securities | 1,797,588,000 |  | 1,797,588,000 |  |
Available for sale debt securities, Estimated Fair Value Disclosures |  |  |  |  |
Fair value of available for sale investment securities pledged | $ 1,501,836,000 |  | $ 1,501,836,000 |  |

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