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Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract] |  |
Proceeds received from sales of marketable securities | $ 15.1 | $ 13.8
Net realized gains (losses) on sale of marketable securities | 0.5 | $ 2.8
Affiliate sponsored investment products |  |
Investment [Line Items] |  |
Fair value of deconsolidated investment in affiliate | $ 84.3 |

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- Definition Marketable Securities, Fair Value, Deconsolidation + References No definition available. + Details
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- Definition Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 12 -Sentence Column A + Details
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- Definition Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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- Definition The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period. + References No definition available. + Details
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- Details
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