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Investment Securities - Schedule of Pledged and Transferred Securities (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
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Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | $ 938,959 | $ 234,226
State of California |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 288,664 | 232,540
Public deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 287,436 | 231,307
Trust deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 666 | 669
Internal checking account |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 562 | 564
Bankruptcy trustee deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 1,151 | 1,686
Pledged to FHLB Securities-Backed Credit Program |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 383,484 | 0
Pledged to the Federal Reserve "BTFP" |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | $ 265,660 | $ 0

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