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Inventories
3 Months Ended
Mar. 31, 2019
Inventory, Net [Abstract]  
Inventories
Inventories

Inventories consist of the following:
 
March 31, 2019
 
December 31, 2018
Raw materials
$
93.9

 
$
100.8

Work-in-process
50.0

 
49.5

Finished goods
35.9

 
47.3

Operating and other supplies
147.6

 
146.2

Total inventories
$
327.4

 
$
343.8


Inventories are stated at the lower of cost or Net Realizable Value ("NRV") using the first-in, first-out ("FIFO") or the weighted average cost method.