Segment and Geographical Area Information, Income Taxes Paid by Geographical Area (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information
Income taxes paid	$ 2.7	$ 0.3	$ 2.9	$ 0.5
Domestic
Segment Reporting Information
Income taxes paid	0.7	0.3	0.9	0.4
Foreign
Segment Reporting Information
Income taxes paid	$ 2.0	$ 0.0	$ 2.0	$ 0.1