Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 19.5	$ 17.4
Operating Leases, Future Minimum Payments, Due in Two Years	20.3	13.8
Operating Leases, Future Minimum Payments, Due in Three Years	18.1	9.1
Operating Leases, Future Minimum Payments, Due in Four Years	14.1	7.4
Operating Leases, Future Minimum Payments, Due in Five Years	8.9	4.5
Operating Leases, Future Minimum Payments, Due Thereafter	$ 0.5	$ 0.0