Revenue Changes in Contract Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Contract Liabilities [Roll Forward]
Contract liabilities	$ 20.0		$ 26.8
Revenue recognized that was included in the contract liability balance at the beginning of the period	(9.1)		(18.5)
Increases due to cash received, excluding amounts recognized as revenue during the period	5.7		8.3
Contract liabilities	$ 16.6		$ 16.6
ASC 605 [Member]
Contract Liabilities [Roll Forward]
Contract liabilities		$ 8.0		$ 13.7
Revenue recognized that was included in the contract liability balance at the beginning of the period		(7.1)		(13.6)
Increases due to cash received, excluding amounts recognized as revenue during the period		5.0		5.8
Contract liabilities		$ 5.9		$ 5.9