Discontinued Operations - Operating Results of the Discontinued Operations (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating costs and expenses:
Income (loss) from discontinued operations		$ 14.7	$ (20.7)	$ 29.1
Provision for (benefit from) income taxes of discontinued operations		2.7	(6.8)	10.7
Net income (loss) from discontinued operations		12.0	(13.9)	18.4
Aromatics [Member] | Discontinued Operations Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales		426.2	759.9	898.8
Operating costs and expenses:
Cost of sales		429.4	775.8	865.0
Selling, general and administrative expenses		3.6	4.8	4.7
Total operating costs and expenses		433.0	780.6	869.7
Operating income (loss) from discontinued operations		(6.8)	(20.7)	29.1
Net gain from the sale of aromatics	$ 5.3	21.5
Income (loss) from discontinued operations		14.7	(20.7)	29.1
Provision for (benefit from) income taxes of discontinued operations		2.7	(6.8)	10.7
Net income (loss) from discontinued operations		$ 12.0	$ (13.9)	$ 18.4