Leases - Lease Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease Cost
Operating lease costs	$ 15.9	$ 17.1	$ 31.6	$ 30.6
Short-term lease costs (1)	6.1	3.7	13.7	7.3
Sublease income	(2.0)	(2.8)	(3.9)	(4.5)
Net lease costs	20.0	18.0	41.4	33.4
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	(15.9)	(17.1)	(31.6)	(30.6)
Non-cash lease liability arising from obtaining right of use assets during the period	$ 15.4	$ 8.1	$ 22.2	$ 8.1
Weighted-average remaining lease term (years) operating leases	6 years 4 months 24 days		6 years 4 months 24 days
Weighted-average discount rate operating leases (2)	6.00%		6.00%