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Investment Securities - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
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Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | $ 937,729 | $ 938,959
State of California |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 279,339 | 288,664
Public deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 277,095 | 287,436
Trust deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 934 | 666
Internal checking account |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 1,310 | 562
Bankruptcy trustee deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 729 | 1,151
FHLB Securities Backed Credit Program |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 288,162 | 383,484
FRBSF short-term borrowings under the BTFP |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | 0 | 265,660
Federal Reserve Discount Window |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Available-for-sale securities pledged as collateral | $ 369,499 | $ 0

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(11)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481444/860-30-45-1 + Details
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