Commitment and Contingencies - Future Minimum Payments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Operating leases
2018	$ 19.1
2019	13.5
2020	9.4
2021	5.8
2022	2.7
Later years	6.4
Minimum lease payments	56.9
Capital leases
2018	6.1
2019	6.1
2020	6.1
2021	6.1
2022	6.1
Later years	107.8
Minimum lease payments	138.3
Less: amount representing interest	(58.3)
Capital lease obligations	$ 80.0	$ 80.0