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Fair Value Measurements - Quantitative Information used in Valuing Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) - Affiliate equity repurchase obligations - Discounted cash flow $ in Millions	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair Value	$ 69.9	$ 19.8
Growth rates | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	(0.01)	(0.09)
Growth rates | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.08	0.07
Growth rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.07	0.05
Discount rates | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.14	0.14
Discount rates | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.16	0.17
Discount rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.15	0.15

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Fair value of financial and nonfinancial obligations.

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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 (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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