Leases Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Lease, Cost [Abstract]
Operating lease cost	$ 3.1		$ 6.3
Short-term lease cost	0.2		0.4
Variable lease cost	0.9		1.5
Total lease cost	$ 4.2	$ 3.4	$ 8.2	$ 7.1