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Investment Securities (Investments Gross Unrealized Losses and Fair Value) (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | $ 768,267 | $ 29,087
Securities available for sale, Less than 12 months, Unrealized Losses | 11,822 | 68
Securities available for sale, 12 months or longer, Fair Value | 16,849 | 8
Securities available for sale, 12 months or longer, Unrealized Losses | 541 |
Securities available for sale, Fair Value, Total | 785,116 | 29,095
Securities available for sale, Unrealized Losses, Total | 12,363 | 68
Total Securities, Less than 12 months, Fair Value | 768,267 | 29,087
Total Securities, Less than 12 months, Unrealized Losses | 11,822 | 68
Total Securities, 12 months or longer, Fair Value | 16,849 | 8
Total Securities, 12 months or longer, Unrealized Losses | 541 |
Total Securities, Fair Value | 785,116 | 29,095
Total Securities, Unrealized Losses | 12,363 | 68
Collateralized Mortgage Obligations [Member] | Federal National Mortgage Association [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 7,818 |
Securities available for sale, Less than 12 months, Unrealized Losses | 132 |
Securities available for sale, 12 months or longer, Fair Value |  | 8
Securities available for sale, Fair Value, Total | 7,818 | 8
Securities available for sale, Unrealized Losses, Total | 132 |
Collateralized Mortgage Obligations [Member] | Federal Home Loan Mortgage Corporation [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 16,190 |
Securities available for sale, Less than 12 months, Unrealized Losses | 128 |
Securities available for sale, Fair Value, Total | 16,190 |
Securities available for sale, Unrealized Losses, Total | 128 |
Mortgage-Backed Securities [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 768,267 | 29,087
Securities available for sale, Less than 12 months, Unrealized Losses | 11,822 | 68
Securities available for sale, 12 months or longer, Fair Value | 16,849 | 8
Securities available for sale, 12 months or longer, Unrealized Losses | 541 |
Securities available for sale, Fair Value, Total | 785,116 | 29,095
Securities available for sale, Unrealized Losses, Total | 12,363 | 68
Mortgage-Backed Securities [Member] | Federal National Mortgage Association [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 328,931 | 18,155
Securities available for sale, Less than 12 months, Unrealized Losses | 4,650 | 44
Securities available for sale, 12 months or longer, Fair Value | 9,173 |
Securities available for sale, Fair Value, Total | 338,104 | 18,155
Securities available for sale, Unrealized Losses, Total | 4,973 | 44
Mortgage-Backed Securities [Member] | Federal Home Loan Mortgage Corporation [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 335,977 | 10,932
Securities available for sale, Less than 12 months, Unrealized Losses | 5,977 | 24
Securities available for sale, 12 months or longer, Fair Value | 7,676 |
Securities available for sale, 12 months or longer, Unrealized Losses | 218 |
Securities available for sale, Fair Value, Total | 343,653 | 10,932
Securities available for sale, Unrealized Losses, Total | 6,195 | $ 24
Mortgage-Backed Securities [Member] | Government National Mortgage Association [Member] |  |
Schedule of Debt Securities Available For Sale and Held To Maturity Securities [Line Item] |  |
Securities available for sale, Less than 12 months, Fair Value | 79,351 |
Securities available for sale, Less than 12 months, Unrealized Losses | 935 |
Securities available for sale, Fair Value, Total | 79,351 |
Securities available for sale, Unrealized Losses, Total | $ 935 |

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