Leases - Lease Cost and Other Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Finance Leases [Abstract]
Amortization of ROU assets	$ 2.6	$ 2.8	$ 5.2	$ 5.5
Interest on lease liabilities	0.4	0.4	0.8	0.9
Operating leases	7.6	7.8	15.3	15.9
Short-term lease cost	1.4	0.8	2.5	1.7
Variable lease cost	0.8	1.2	2.7	2.8
Total lease cost	$ 12.8	$ 13.0	26.5	26.8
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows - finance leases			2.4	2.3
Operating cash flows - operating leases			15.5	17.5
Financing cash flows - finance leases			5.1	5.9
Right-Of-Use Asset Obtained In Exchange For Lease Liability [Abstract]
ROU assets obtained in exchange for new finance lease liabilities			4.2	5.1
ROU assets obtained in exchange for new operating lease liabilities			$ 9.2	$ 9.0
Finance leases
Remaining lease term (in years)	5 years 10 months 24 days	6 years 1 month 6 days	5 years 10 months 24 days	6 years 1 month 6 days
Discount rate	4.60%	4.80%	4.60%	4.80%
Operating leases
Remaining lease term (in years)	4 years 6 months	4 years 9 months 18 days	4 years 6 months	4 years 9 months 18 days
Discount rate	4.80%	5.10%	4.80%	5.10%