Leases (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net	$ 31.1		$ 31.1		$ 36.8
Operating leases	14.5		14.5		14.7
Operating leases	22.0		22.0		28.5
Total operating lease liabilities	36.5		36.5		43.2
Finance Lease, Right-of-Use Asset, before Accumulated Amortization	12.1		12.1		13.3
Property, plant and equipment	3,788.5		3,788.5		3,759.6
Finance Lease, Right-of-Use Asset, Accumulated Amortization	8.5		8.5		7.9
Less: accumulated depreciation	962.7		962.7		842.5
Finance Lease, Right-of-Use Asset, after Accumulated Amortization	3.6		3.6		5.4
Property, plant and equipment, net	2,825.8		2,825.8		2,917.1
Finance leases	2.1		2.1		2.9
Finance Lease, Liability, Noncurrent	1.2		1.2		1.9
Finance Lease, Liability	3.3		3.3		$ 4.8
Operating lease expense	3.7	$ 5.8	12.8	$ 20.4
Finance lease expense	$ 0.8	$ 0.9	$ 2.6	$ 3.1
Operating lease, liability, current, extensible enumeration	Accrued expenses and other liabilities		Accrued expenses and other liabilities		Accrued expenses and other liabilities
Finance lease, liability, noncurrent, extensible enumeration	Other long-term liabilities		Other long-term liabilities		Other long-term liabilities
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other liabilities		Accrued expenses and other liabilities		Accrued expenses and other liabilities
Operating lease, liability, noncurrent, extensible enumeration	Other long-term liabilities		Other long-term liabilities		Other long-term liabilities