Leases - Lease Obligations (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Finance leases - ROU assets	$ 58.5	$ 58.2
Finance leases - Accumulated depreciation	(23.9)	(22.6)
Operating leases - ROU assets	132.8	127.4
Operating leases - Accumulated depreciation	(62.1)	(51.3)
Total lease assets	105.3	111.7
Finance leases	(11.2)	(10.5)
Operating leases	(23.7)	(24.3)
Finance leases	(21.8)	(23.9)
Operating leases	(48.8)	(53.2)
Total lease liabilities	$ (105.5)	$ (111.9)
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other non-current assets	Other non-current assets
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtNoncurrent	us-gaap:LongTermDebtNoncurrent
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtCurrent	us-gaap:LongTermDebtCurrent