Leases - Lease Cost and Other Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Finance Leases [Abstract]
Amortization of ROU assets	$ 2.8	$ 2.0	$ 5.5	$ 4.1
Interest on lease liabilities	0.4	0.5	0.9	1.0
Operating leases	7.8	7.9	15.9	16.3
Short-term lease cost	0.8	1.0	1.7	1.9
Variable lease cost	1.2	2.1	2.8	3.1
Total lease cost	$ 13.0	$ 13.5	26.8	26.4
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows - finance leases			2.3	2.0
Operating cash flows - operating leases			17.5	17.3
Financing cash flows - finance leases			5.9	3.7
Right-Of-Use Asset Obtained In Exchange For Lease Liability [Abstract]
ROU assets obtained in exchange for new finance lease liabilities			5.1	9.0
ROU assets obtained in exchange for new operating lease liabilities			$ 9.0	$ 4.9
Finance leases
Remaining lease term (in years)	6 years 1 month 6 days	7 years 3 months 18 days	6 years 1 month 6 days	7 years 3 months 18 days
Discount rate	4.80%	5.40%	4.80%	5.40%
Operating leases
Remaining lease term (in years)	4 years 9 months 18 days	5 years	4 years 9 months 18 days	5 years
Discount rate	5.10%	5.50%	5.10%	5.50%