Derivatives and Fair Value Measurements - Long-term debt (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net carrying amount	$ 1,418.1	$ 1,547.8
Carrying amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total debt at par value	1,469.9	1,591.3
Less: Unamortized debt issuance costs and original issue discount	(51.8)	(43.5)
Net carrying amount	1,418.1	1,547.8
Estimated fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair value	$ 1,179.4	$ 987.6