Investments - Realized and Unrealized Gains (Losses) Earned from Investments of Consolidated Funds (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments [Abstract]
Realized gains (losses)	$ (9.6)	$ 1.9	$ (49.9)	$ (9.5)
Net change in unrealized gains (losses)	172.7	(1.3)	(169.3)	28.3
Total	$ 163.1	$ 0.6	$ (219.2)	$ 18.8

Amount of realized gain (loss) on investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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