Summary of Significant Accounting Policies - Maturities of Lease Liabilities, Topic 840 (Details) $ in Millions	Dec. 31, 2018 USD ($)
Finance Leases
2019	$ 1.6
2020	1.6
2021	1.6
2022	1.0
2023	0.0
Thereafter	0.0
Total	5.8
Operating Leases
2019	48.5
2020	42.1
2021	30.0
2022	20.8
2023	14.3
Thereafter	24.4
Total	180.1
Minimum sublease rentals due in the future under noncancelable operating leases	$ 2.7