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Derivative Instruments and Hedging Activities - Notional amounts, fair values and classification (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	May 09, 2018
Derivatives
Derivative current liabilities, fair value	$ 3.8	$ 9.4
Interest rate swaps \| Cash flow hedging
Derivatives
Notional amount	1,320.1	1,323.5	$ 1,361.2
Interest rate swaps \| Cash flow hedging \| Accrued Liabilities and Other
Derivatives
Derivative current liabilities, fair value	$ 3.8	$ 9.4