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Investment Securities - Securities Sold, Pledged as Collateral and Transfers (Details) - USD ($) $ in Thousands |  | 12 Months Ended
--- | --- | ---
Feb. 24, 2017 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Available-for-sale: |  |  |  |
Sales proceeds |  | $ 55,408 | $ 68,673 | $ 2,099
Gross realized gains |  | 46 | 458 | 7
Gross realized losses |  | (231) | (64) | (1)
Held-to-maturity: |  |  |  |
Sales proceeds |  | 0 | 1,265 | 1,015
Gross realized gains |  | 0 | 32 | 73
Gross realized losses |  | 0 | 0 | 0
Securities transferred from available-for-sale to held-to-maturity | $ 129,000 | 128,965 | 0 | 0
Unrealized pre-tax loss from transfer of available-for-sale securities to held-to-maturity | $ 3,000 |  |  |
Amortization of net unrealized losses on securities transferred from available-for-sale to held-to-maturity |  | 426 | 21 | $ 61
State of California |  |  |  |
Available-for-sale: |  |  |  |
Available-for-sale securities pledged as collateral |  | 108,590 | 109,126 |
Public Deposits |  |  |  |
Available-for-sale: |  |  |  |
Available-for-sale securities pledged as collateral |  | 107,829 | 108,304 |
Trust Deposits |  |  |  |
Available-for-sale: |  |  |  |
Available-for-sale securities pledged as collateral |  | 761 | 822 |
Internal checking account |  |  |  |
Available-for-sale: |  |  |  |
Available-for-sale securities pledged as collateral |  | $ 2,026 | $ 2,146 |

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- Definition Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729 + Details
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