Leases - Lease Cost (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Lease Cost
Operating lease costs	$ 13.5	$ 44.1
Short-term lease costs (1)	4.0	11.3
Sublease income	(1.9)	(6.4)
Net lease costs	15.6	49.0
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	(13.5)	(44.1)
Non-cash lease liability arising from obtaining right of use assets during the period	$ 1.5	$ 9.6
Weighted-average remaining lease term (years) operating leases	6 years 8 months 8 days	6 years 8 months 8 days
Weighted-average discount rate operating leases (2)	6.20%	6.20%