Discontinued Operations - Operating Results of the Discontinued Operations (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating costs and expenses:
Loss from discontinued operations	$ (1.7)		$ (1.7)	$ (33.1)	$ (8.9)
Benefit from income taxes of discontinued operations	(1.7)		(0.8)	(10.1)	(1.6)
Net loss from discontinued operations			(0.9)	(23.0)	(7.3)
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	1.3		189.3	33.6	352.3
Operating costs and expenses:
Cost of sales	2.6		184.2	35.7	348.3
Selling, general and administrative expenses	0.4		5.4	4.5	10.7
Restructuring and divestiture costs					0.3
Total operating costs and expenses	3.0		189.6	40.2	359.3
Operating loss from discontinued operations	(1.7)		(0.3)	(6.6)	(7.0)
Interest expense, net			(1.2)	(1.1)	(2.3)
Foreign currency exchange gain (loss)			(0.2)	(0.3)	0.4
Net loss from the sale of business		$ 5.3		(25.1)
Loss from discontinued operations	(1.7)		(1.7)	(33.1)	(8.9)
Benefit from income taxes of discontinued operations	$ (1.7)		(0.8)	(10.1)	(1.6)
Net loss from discontinued operations			$ (0.9)	$ (23.0)	$ (7.3)