Financial Instruments - Carrying Amount and Estimated Fair Value of Asset (Liability) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Carrying Amount | Short-term and Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure of debt instrument	$ 849.1	$ 847.2
Carrying Amount | New Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure of debt instrument	2,724.8	2,433.9
Fair Value | Short-term and Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure of debt instrument	1,052.7	1,056.1
Fair Value | New Term Loan Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value disclosure of debt instrument	$ 2,813.9	$ 2,476.2