Summary of Significant Accounting Policies - Components of Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 307.8	$ 279.8
Work in process	13.9	12.6
Finished goods	199.0	217.0
Supplies and materials	274.9	253.1
Inventories	$ 795.6	$ 762.5

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount before valuation and LIFO reserves of raw materials expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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Amount before valuation and LIFO reserves of other supplies used within the manufacturing or production process expected to be consumed within one year or operating cycle, if longer.

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