Leases - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease Cost
Amortization of Right-of-Use Assets - Finance Leases	$ 0.0	$ 0.1	$ 0.1	$ 0.2
Operating Lease Cost	5.9	5.2	11.0	10.8
Variable Lease, Cost	0.1		0.1
Short-Term Lease Cost	0.7	0.0	1.6	0.0
Total Lease Cost	$ 6.7	$ 5.3	$ 12.8	$ 11.0