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Investment Securities - Hedge Funds and Private Equity Funds (Details) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2020 USD ($) | Sep. 30, 2020 USD ($) fund | Dec. 31, 2019 USD ($)
Private equity funds |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |
Number of investments | fund |  | 14 |
Hedge and private equity funds included in other long-term investments |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |
Largest single fund investment |  | $ 23.7 | $ 54.6
Hedge funds | Hedge funds |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |
Transfer from investments | $ 45.6 |  |

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