Restructuring Costs - Summary of Activity in Accrued Workforce Reduction (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2015
Amounts recognized in our Consolidated Balance Sheet at the end of the period:
Current liability					$ 5.3
Chemicals | Employee Severance
Restructuring Cost And Reserve [Line Items]
Workforce reduction costs accrued	$ 0.2	$ 0.4	$ 21.1	$ 21.7
Workforce reduction costs paid				(15.9)
Currency translation adjustments, net				(0.2)
Accrued workforce reduction costs, ending balance	5.6			5.6
Amounts recognized in our Consolidated Balance Sheet at the end of the period:
Current liability					5.3
Noncurrent liability					0.3
Restructuring Reserve	$ 5.6			$ 5.6	$ 5.6