Business segment information - Segment Operating Performance (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$ 499.2	$ 582.8
Cost of sales	486.3	322.4
Gross margin	12.9	260.4
Operating income (loss)	(45.2)	203.3
Equity in earnings of investee	(0.3)	0.1
Securities earnings	6.6	7.1
Insurance recoveries	0.6	1.1
Loss on prepayment of debt	(6.6)
General expenses, net	(9.7)	(20.3)
Interest expense	(15.4)	(13.5)
Income (loss) from continuing operations before income taxes	(70.0)	177.8
Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales	463.6	561.3
Cost of sales	460.3	300.4
Gross margin	3.3	260.9
Operating income (loss)	(45.1)	211.3
Component Products [Member]
Segment Reporting Information [Line Items]
Net sales	21.5	20.4
Cost of sales	15.5	14.4
Gross margin	6.0	6.0
Operating income (loss)	1.5	1.6
Waste Management [Member]
Segment Reporting Information [Line Items]
Net sales	14.1	1.1
Cost of sales	10.5	7.6
Gross margin	3.6	(6.5)
Operating income (loss)	$ (1.6)	$ (9.6)