Investments and Related Party Transactions - Schedule of Related Party Balances (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Chlorovinyls [Member]
Schedule of Investments [Line Items]
Equity method investments	$ 15.8	$ 11.0	$ 11.7
Receivables due from affiliates	4.1	5.5	5.0
Amounts due to affiliates	0.2	0.4	1.9
Equity in earnings from equity method investments	0.5	0.6	0.8
Chlorovinyls [Member] | Sales [Member]
Schedule of Investments [Line Items]
Amounts due to affiliates	17.1	16.9	10.8
Building Products [Member]
Schedule of Investments [Line Items]
Equity method investments	0.7	0.8	0.6
Receivables due from affiliates	1.2	1.2	1.0
Amounts due to affiliates	$ 8.0	8.8	$ 11.6
Equity in earnings from equity method investments		$ 0.3