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Investment Securities - Narrative (Details) $ in Thousands | Sep. 30, 2020 USD ($) instrument | Dec. 31, 2019 USD ($)
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Investments, Debt and Equity Securities [Abstract] |  |
Carrying value of securities pledged as collateral | $ 989,906 | $ 503,427
Book value of securities sold under agreements to repurchase | 177,543 | 182,856
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Gross unrealized losses | 187 | 2,211
Held-to-maturity unrealized losses | 1,278 | 545
State and municipal |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Gross unrealized losses | $ 187 | 807
Number of securities in unrealized loss positions | instrument | 13 |
Held-to-maturity unrealized losses | $ 1,240 | 107
Held-to-maturity, number of securities in unrealized loss positions | instrument | 71 |
U.S. Government-sponsored agency securities |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Gross unrealized losses | $ 0 | 0
Held-to-maturity unrealized losses | $ 33 | 37
Held-to-maturity, number of securities in unrealized loss positions | instrument | 2 |
Foreign investment |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Held-to-maturity unrealized losses | $ 2 | 0
Held-to-maturity, number of securities in unrealized loss positions | instrument | 1 |
U.S. Government-sponsored mortgage-backed securities |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |
Gross unrealized losses | $ 0 | 1,404
Held-to-maturity unrealized losses | $ 3 | $ 401
Held-to-maturity, number of securities in unrealized loss positions | instrument | 1 |

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- Definition Carrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details
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