Inventories, Net - Schedule of Inventories Net (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Finished products	$ 683.2	$ 667.0
Products in process	25.6	37.1
Raw materials	55.9	35.3
Supplies and expendable parts	152.0	149.9
Inventories, Gross	916.7	889.3
Less: Allowances	(199.2)	(180.3)
Total	$ 717.5	$ 709.0

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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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