Supplemental Balance Sheet Information - Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
LIFO
Raw materials	$ 44.4	$ 43.9
Work in process	34.8	32.2
Finished goods	60.7	73.5
Supplies and other	0.0	0.0
Inventory, gross	139.9	149.6
Excess of FIFO or weighted-average cost over LIFO cost	(7.0)	(7.5)
Inventories, net	132.9	142.1
Non- LIFO
Raw materials	2.0	3.1
Work in process	0.0	0.1
Finished goods	17.2	16.9
Supplies and other	6.3	6.7
Inventory, gross	25.5	26.8
Inventories, net	25.5	26.8
Inventory, Net
Raw materials	46.4	47.0
Work in process	34.8	32.3
Finished goods	77.9	90.4
Supplies and other	6.3	6.7
Inventory, gross	165.4	176.4
Excess of FIFO or weighted-average cost over LIFO cost	(7.0)	(7.5)
Inventory, net	$ 158.4	$ 168.9