Fair Value Measurements and the Fair Value Option - Schedule of Changes in Level 3 Investments (Details) - Equity Method Investments [Member] - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 1,107.4	$ 662.2
Unrealized and realized gains	24.8	41.2
Unrealized and realized losses	(16.4)	(6.0)
Contributions	44.4	19.6
Distributions	(62.0)	(7.4)
Non-cash distributions	(16.6)	0.4
Ending Balance	$ 1,081.6	$ 710.0

Fair Value, Measurements with Unobservable Inputs Reconciliation Recurring Basis, Asset, Other

No definition available.

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- Definition

Fair Value, Measurements with Unobservable Inputs Reconciliation Recurring Basis, Asset, Unrealized and Realized Gains

+ References

No definition available.

+ Details

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- Definition

Fair Value, Measurements with Unobservable Inputs Reconciliation Recurring Basis, Asset, Unrealized and Realized Losses

+ References

No definition available.

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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