Fair Value Measurements - Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 12.6	$ 6.4
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	63.5	55.6
Debt securities	12.6	6.4
Redeemable noncontrolling interests	239.6	261.7
Fair Value, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Debt securities	12.6	6.4
Redeemable noncontrolling interests	0.0	0.0
Fair Value, Recurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	63.5	55.6
Debt securities	0.0	0.0
Redeemable noncontrolling interests	0.0	0.0
Fair Value, Recurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0.0	0.0
Debt securities	0.0	0.0
Redeemable noncontrolling interests	$ 239.6	$ 261.7