Goodwill and Other Intangible Assets - Detail of the Changes Made to Goodwill (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Gross goodwill at the beginning of the period	$ 1,926.2
Goodwill write-downs from sale of assets	(3.3)
Foreign currency translation adjustment	7.4
Gross goodwill at the end of the period	1,930.3
Accumulated impairment losses	(1,074.1)	$ (1,074.1)
Net goodwill at the end of the period	856.2	852.1
Chlorovinyls [Member]
Goodwill [Line Items]
Gross goodwill at the beginning of the period	1,766.0
Goodwill write-downs from sale of assets	(3.3)
Foreign currency translation adjustment	7.4
Gross goodwill at the end of the period	1,770.1
Accumulated impairment losses	(923.7)	(923.7)
Net goodwill at the end of the period	846.4	842.3
Building Products [Member]
Goodwill [Line Items]
Gross goodwill at the beginning of the period	160.2
Gross goodwill at the end of the period	160.2
Accumulated impairment losses	(150.4)	(150.4)
Net goodwill at the end of the period	$ 9.8	$ 9.8