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Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Abstract]
Proceeds from sale of investments in marketable securities	$ 38.0	$ 81.4
Net gains on sales of marketable securities	1.1	6.9
Affiliate sponsored investment products
Marketable Securities [Line Items]
Fair value of deconsolidated affiliate	$ 38.1	$ 105.1

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- Definition

Marketable Securities, Fair Value, Deconsolidation

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No definition available.

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- Definition

Line items represent financial 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.

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No definition available.

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- Definition

Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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No definition available.

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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.

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No definition available.

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