Recent Accounting Pronouncements New Accounting Standards - Effect fo changes due to Adoption of ASU 2016-18 (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 135.4	$ 167.2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations	170.1	95.1	$ 85.5	$ 83.0
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		10.9
Effect of exchange rate changes on cash flows	$ (0.6)	1.2
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		3.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations		37.3		34.3
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		3.0
Effect of exchange rate changes on cash flows		0.0
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		164.2
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations		57.8		$ 48.7
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		7.9
Effect of exchange rate changes on cash flows		$ 1.2