Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes due 2025	$ 411.1	$ 0.0
Long-term debt	907.7	1,321.0
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes due 2025	902.7	0.0
Long-term debt	907.7	1,321.0
Cross-currency swap derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	61.8	8.9
Cross-currency swap derivative contracts | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	61.8	8.9
Cross-currency swap derivative contracts | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	61.8	8.9
Interest rate swap derivative contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0.1
Derivative liabilities	8.3
Interest rate swap derivative contracts | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.1
Derivative liabilities	8.3	0.0
Interest rate swap derivative contracts | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.0	0.1
Derivative liabilities	$ 8.3	$ 0.0