Derivatives, Hedging Programs and Other Financial Instruments - Schedule of Other Financial Assets Classifies under Appropriate Level of Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 750.1	$ 264.3
Total	750.1	343.0
Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		78.7
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	750.1	28.2
Total	750.1	28.2
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.0	236.1
Total	0.0	314.8
Level 2 | Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		$ 78.7
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	0.0
Total	$ 0.0