Leases - Financing leases (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Plant, Property and Equipment, Net
Plant, property and equipment, net	$ 1,058.5	$ 1,053.4
Accumulated amortization	(1,844.1)	$ (1,755.6)
Finance lease obligations, Current	$ 4.1
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Long-term Debt, Current Maturities
Finance lease obligations, Noncurrent	$ 8.0
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term Debt, Excluding Current Maturities
Finance leased assets
Plant, Property and Equipment, Net
Plant, property and equipment, net	$ 11.8
Accumulated amortization	$ (1.9)

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

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Indicates line item in statement of financial position that includes current finance lease liability.

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Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

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Indicates line item in statement of financial position that includes noncurrent finance lease liability.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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