Supplemental Balance Sheet Information - Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
LIFO
Raw materials	$ 57.3	$ 46.3
Work in process	31.6	30.4
Finished goods	75.0	49.5
Supplies and other	0.0	0.0
Inventory, gross	163.9	126.2
Excess of FIFO or weighted-average cost over LIFO cost	(7.4)	(9.9)
Inventories, net	156.5	116.3
Non- LIFO
Raw materials	3.2	2.9
Work in process	0.6	0.5
Finished goods	18.0	21.7
Supplies and other	5.8	4.5
Inventory, gross	27.6	29.6
Inventories, net	27.6	29.6
Inventory, Net
Raw materials	60.5	49.2
Work in process	32.2	30.9
Finished goods	93.0	71.2
Supplies and other	5.8	4.5
Inventory, gross	191.5	155.8
Excess of FIFO or weighted-average cost over LIFO cost	(7.4)	(9.9)
Inventory, net	$ 184.1	$ 145.9