Other Assets (Additional Information) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Other Assets [Line Items]
Amortization expense on intangible assets, included in other assets	$ 9,542	$ 9,283	$ 28,604	$ 26,566
Olefins
Other Assets [Line Items]
Goodwill	29,990		29,990		$ 29,990
Vinyls
Other Assets [Line Items]
Goodwill	$ 32,026		$ 32,026		$ 32,026