Commitments and Contingencies Long-term Operating lease commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating lease commitments [Abstract]
Operating Leases, Rent Expense	$ 30.3	$ 24.9	$ 21.7
Operating Leases, Future Minimum Payments Due, Next Twelve Months	17.4
Operating Leases, Future Minimum Payments, Due in Two Years	13.8
Operating Leases, Future Minimum Payments, Due in Three Years	9.1
Operating Leases, Future Minimum Payments, Due in Four Years	7.4
Operating Leases, Future Minimum Payments, Due in Five Years	4.5
Operating Leases, Future Minimum Payments, Due Thereafter	$ 0.0