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Allowance for Credit Losses - Schedule of Held-to-Maturity Debt Securities by Credit Quality Indicator (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022 | Sep. 30, 2022
--- | --- | --- | ---
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
Amortized Cost | $ 3,909,531 | $ 3,641,055 | $ 3,390,152
Less: Allowance for credit losses | (381) | (488) | (310)
Held-to-maturity securities, net of allowance for credit losses | 3,909,150 | 3,640,567 | 3,389,842
U.S. government agencies |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 160,000 |  |
2021 | 147,808 |  |
2020 | 25,000 |  |
2019 | 4,000 |  |
Prior | 2,790 |  |
Amortized Cost | 339,598 | 339,614 | 314,618
U.S. government agencies | 1-4 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 160,000 |  |
2021 | 147,808 |  |
2020 | 25,000 |  |
2019 | 4,000 |  |
Prior | 2,790 |  |
Amortized Cost | 339,598 |  |
U.S. government agencies | 5-7 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
U.S. government agencies | 8-10 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Municipal |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 4,176 |  |
2022 | 1,040 |  |
2021 | 6,932 |  |
2020 | 259 |  |
2019 | 614 |  |
Prior | 163,241 |  |
Amortized Cost | 176,262 | $ 179,027 | $ 180,304
Municipal | 1-4 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 4,176 |  |
2022 | 1,040 |  |
2021 | 6,932 |  |
2020 | 259 |  |
2019 | 614 |  |
Prior | 163,241 |  |
Amortized Cost | 176,262 |  |
Municipal | 5-7 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Municipal | 8-10 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Mortgage-backed securities |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 393,193 |  |
2022 | 583,401 |  |
2021 | 2,359,360 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 3,335,954 |  |
Mortgage-backed securities | 1-4 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 393,193 |  |
2022 | 583,401 |  |
2021 | 2,359,360 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 3,335,954 |  |
Mortgage-backed securities | 5-7 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Mortgage-backed securities | 8-10 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Corporate notes |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 14,965 |  |
2021 | 0 |  |
2020 | 6,008 |  |
2019 | 7,248 |  |
Prior | 29,496 |  |
Amortized Cost | 57,717 |  |
Corporate notes | 1-4 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 14,965 |  |
2021 | 0 |  |
2020 | 6,008 |  |
2019 | 7,248 |  |
Prior | 29,496 |  |
Amortized Cost | 57,717 |  |
Corporate notes | 5-7 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | 0 |  |
Corporate notes | 8-10 internal grade |  |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |  |
2023 | 0 |  |
2022 | 0 |  |
2021 | 0 |  |
2020 | 0 |  |
2019 | 0 |  |
Prior | 0 |  |
Amortized Cost | $ 0 |  |

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