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Inventories
6 Months Ended
Jun. 30, 2019
Inventory, Net [Abstract]  
Inventories
Inventories

Inventories consist of the following:
 
June 30, 2019
 
December 31, 2018
Raw materials
$
100.3

 
$
100.8

Work-in-process
51.5

 
49.5

Finished goods
33.8

 
47.3

Operating and other supplies
153.6

 
146.2

Total inventories
$
339.2

 
$
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.