Restructuring Costs - Summary of Activity in Accrued Workforce Reduction (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2015	Sep. 30, 2015	Sep. 30, 2015
Amounts recognized in our Condensed Consolidated Balance Sheet at the end of the period:
Current liability			$ 15.2
Noncurrent liability			3.0
Chemicals | Employee Severance
Restructuring Cost And Reserve [Line Items]
Workforce reduction costs accrued	$ 21.1	$ 21.5
Workforce reduction costs paid		(3.8)
Currency translation adjustments, net		0.5
Accrued workforce reduction costs at September 30, 2015		18.2
Amounts recognized in our Condensed Consolidated Balance Sheet at the end of the period:
Current liability			15.2
Noncurrent liability			3.0
Restructuring Reserve		$ 18.2	$ 18.2