Discontinued Operations - Depreciation, Amortization and Capital Expenditures Associated with Discontinued Operations (Detail) - Aromatics [Member] - Discontinued Operations Disposed of by Sale [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization	$ 1.9	$ 2.0	$ 1.2
Capital expenditures	$ 1.0	$ 8.0	$ 7.1