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Investment Securities - Narrative (Details) $ in Thousands | Dec. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
--- | --- | --- | ---
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |  |
Fair value of investments | $ 395,416 | $ 932,577 |
Unrealized losses on available for sale securities | 2,211 | 14,253 |
Unrealized losses in held to maturity portfolios | 545 | 4,741 |
Carrying value of securities pledged as collateral | 503,427 | 416,155 | $ 475,999
Securities sold under repurchase agreements | 182,856 | 116,691 |
Investments in Debt and Equity Securities, Reported at Less than Historical Cost |  |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |  |
Historical cost | 398,172 | 951,571 |
Fair value of investments | $ 395,416 | $ 932,577 |
Percent of the Corporation's available for sale and held to maturity portfolio | 15.20% | 57.10% |
U.S. Government-Sponsored Mortgage-backed Securities |  |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |  |
Unrealized losses on available for sale securities | $ 1,404 | $ 8,396 |
Available-for-sale number of securities in unrealized loss positions | security | 27 |  |
Unrealized losses in held to maturity portfolios | $ 401 | 3,323 |
Held-to-maturity, number of securities in unrealized loss positions | security | 15 |  |
State and municipal securities |  |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |  |
Unrealized losses on available for sale securities | $ 807 | 5,854 |
Available-for-sale number of securities in unrealized loss positions | security | 38 |  |
Unrealized losses in held to maturity portfolios | $ 107 | 872 |
Held-to-maturity, number of securities in unrealized loss positions | security | 18 |  |
U.S. Government-sponsored agency securities |  |  |
Schedule of Available for sale Securities and Held to maturity Securities [Line Items] |  |  |
Unrealized losses on available for sale securities | $ 0 | 3 |
Unrealized losses in held to maturity portfolios | $ 37 | $ 545 |
Held-to-maturity, number of securities in unrealized loss positions | security | 3 |  |

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