Financial Instruments and Risk Management - Fair Value and Carrying Value of Debt (Details) - Revolving Credit Facility - Term Loan due 2027 at 2.83% and 3.15% at September 30, 2021 and December 31, 2020, respectively. - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value disclosure	$ 2,153.6	$ 2,169.9
Par Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value disclosure	$ 2,167.1	$ 2,183.5