Inventories, Net (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories, Net

	December 31,
	2016		2017
	(In millions)
Raw materials:
Chemicals	$	68.7	$	106.9
Component products		2.7		2.7
Total raw materials		71.4		109.6
Work in process:
Chemicals		22.3		20.8
Component products		9.0		9.8
Total in-process products		31.3		30.6
Finished products:
Chemicals		196.4		192.2
Component products		3.2		2.8
Total finished products		199.6		195.0
Supplies (chemicals)		56.9		63.2
Total	$	359.2	$	398.4