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, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in the balance sheet:
Current liability						$ 1.2	$ 5.3
Chemicals | Employee Severance
Restructuring Cost And Reserve [Line Items]
Balance at beginning of the year				$ 5.6
Workforce reduction costs accrued	$ 0.2	$ 0.4	$ 21.1		$ 21.7
Workforce reduction costs paid				(4.1)	(15.9)
Currency translation adjustments, net				(0.1)	(0.2)
Balance at end of the year	5.6			1.4	5.6
Amounts recognized in the balance sheet:
Current liability						1.2	5.3
Noncurrent liability						0.2	0.3
Restructuring Reserve	$ 5.6			$ 5.6	$ 5.6	$ 1.4	$ 5.6