Revenue Changes in Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Contract Liabilities [Roll Forward]
Beginning balance	$ 19.7	$ 16.1	$ 29.9	$ 30.5
Revenue recognized that was included in the contract liability balance at the beginning of the period	(9.6)	(9.6)	(25.3)	(28.2)
Increases due to consideration received, excluding amounts recognized as revenue during the period	2.4	2.1	7.9	6.3
Ending balance	$ 12.5	$ 8.6	$ 12.5	$ 8.6