Geographic Information (Long-Lived Assets By Geographic Areas) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 974.8	$ 948.1	$ 867.7
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	919.5	899.1	821.1
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	35.9	33.2	32.3
Other foreign countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total long-lived assets	$ 19.4	$ 15.8	$ 14.3