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Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Financial Assets
Other investments	$ 204.0	$ 211.8
Fair Value Measured on a Recurring Basis
Financial Assets
Investments in marketable securities	61.4	59.4
Other investments	8.5
Derivative financial instruments	1.0	7.9
Financial Liabilities
Affiliate equity repurchase obligations	73.3	19.8
Derivative financial instruments	2.6	1.0
Fair Value Measured on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets
Investments in marketable securities	26.3	24.4
Other investments	0.0
Derivative financial instruments	0.0	0.0
Financial Liabilities
Affiliate equity repurchase obligations	0.0	0.0
Derivative financial instruments	0.0	0.0
Fair Value Measured on a Recurring Basis | Significant Other Observable Inputs (Level 2)
Financial Assets
Investments in marketable securities	35.1	35.0
Other investments	0.0
Derivative financial instruments	1.0	7.9
Financial Liabilities
Affiliate equity repurchase obligations	0.0	0.0
Derivative financial instruments	2.6	1.0
Fair Value Measured on a Recurring Basis | Significant Unobservable Inputs (Level 3)
Financial Assets
Investments in marketable securities	0.0	0.0
Other investments	8.5
Derivative financial instruments	0.0	0.0
Financial Liabilities
Affiliate equity repurchase obligations	73.3	19.8
Derivative financial instruments	$ 0.0	$ 0.0

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