Unusual Items - Summary of Unusual Items Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Unusual or Infrequent Item [Line Items]
Loss on debt	$ 0.9	$ 0.0	$ 10.5	$ 0.0
Unusual Items
Unusual or Infrequent Item [Line Items]
Merger costs (component of other expense, net)	7.2	0.0	20.8	0.0
Loss on debt	0.9	0.0	10.5	0.0
Legal related matter (component of other expense, net)	0.0	0.0	0.0	1.8
Total unusual items	$ 8.1	$ 0.0	$ 31.3	$ 1.8