Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Finished products	$ 415.5	$ 400.7	$ 452.0
Work in process	580.5	570.4	580.0
Raw materials and supplies	83.7	80.4	70.4
Total (approximates replacement cost)	1,079.7	1,051.5	1,102.4
Decrease to LIFO cost	(44.2)	(47.4)	(40.1)
Inventories	$ 1,035.5	$ 1,004.1	$ 1,062.3

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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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Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

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Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

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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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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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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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