Other Assets (Additional Information) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Other Assets [Line Items]
Amortization expense on intangible assets, included in other assets	$ 9,578	$ 9,008	$ 19,062	$ 17,284
Olefins
Other Assets [Line Items]
Goodwill	29,990		29,990		$ 29,990
Vinyls
Other Assets [Line Items]
Goodwill	$ 32,026		$ 32,026		$ 32,026