Leases - Costs and SCF (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease, Cost [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 2.7	$ 0.8
Finance Lease, Interest Expense	0.2	0.1
Operating lease cost	21.2	18.2
Variable Lease, Cost	0.4	0.2
Total lease cost	24.5	19.3
Operating Lease, Payments	19.5	17.0
Finance Lease, Interest Payment on Liability	0.2	0.1
Finance Lease, Principal Payments	2.7	0.8
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	20.7	86.2
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 3.0	$ 8.8