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Investments - Details of Investments Carried at Cost (Detail) - USD ($) $ in Thousands | Mar. 31, 2020 | Dec. 31, 2019 | Dec. 27, 2019 | Dec. 31, 2018
--- | --- | --- | --- | ---
Investment [Line Items] |  |  |  |
Investments | $ 11,192 | $ 11,192 |  |
Advisor Engine [Member] | Convertible Preferred Stock [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Investments |  |  |  | $ 25,000
Thesys Group, Inc [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Investments | 3,080 | 3,080 |  |
Securrency Inc [Member] | Convertible Preferred Stock [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Investments | $ 8,112 | $ 8,112 | $ 8,112 |

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- Details
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