Recent Accounting Pronouncements New Accounting Standards - Effect fo changes due to Adoption of ASU 2016-18 (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 162.3	$ 168.4
Cash and cash equivalents	254.6		$ 51.7	$ 73.4	$ 83.0
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect	209.8	(10.2)
Effect of exchange rate changes on cash	$ (0.6)	0.6
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		171.1
Cash and cash equivalents				41.8	48.7
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		(7.5)
Effect of exchange rate changes on cash		0.6
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		(2.7)
Cash and cash equivalents				$ 31.6	$ 34.3
Cash and Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect		(2.7)
Effect of exchange rate changes on cash		$ 0.0