Business Segment Information - Segment Operating Performance (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net sales		$ 514.9	$ 406.8	$ 1,444.0	$ 1,158.9
Cost of sales		346.3	321.5	1,012.7	969.4
Gross margin		168.6	85.3	431.3	189.5
Operating income (loss)		102.6	29.7	70.5	29.2
Securities earnings		7.5	6.8	21.7	20.5
Insurance recoveries		0.1	0.1	0.2	0.4
Termination fee	$ 4.0			4.0
General expenses, net		(7.7)	(9.1)	(34.8)	(29.2)
Loss on prepayment of debt, net		(7.1)		(7.1)
Interest expense		(16.3)	(15.9)	(47.9)	(47.4)
Income (loss) before income taxes		79.1	11.6	6.6	(26.5)
Chemicals
Segment Reporting Information [Line Items]
Net sales		464.5	356.1	1,275.7	1,030.6
Cost of sales		312.9	281.1	891.8	860.6
Gross margin		151.6	75.0	383.9	170.0
Operating income (loss)		93.9	30.1	221.9	45.8
Component Products
Segment Reporting Information [Line Items]
Net sales		26.9	28.4	86.9	82.6
Cost of sales		18.8	19.0	59.6	56.5
Gross margin		8.1	9.4	27.3	26.1
Operating income (loss)		3.4	4.4	12.5	11.5
Waste Management
Segment Reporting Information [Line Items]
Net sales		18.4	13.6	60.4	29.9
Cost of sales		11.2	14.1	45.8	39.4
Gross margin		7.2	(0.5)	14.6	(9.5)
Operating income (loss)		4.0	(5.1)	(167.0)	(23.0)
Real Estate Management And Development
Segment Reporting Information [Line Items]
Net sales		5.1	8.7	21.0	15.8
Cost of sales		3.4	7.3	15.5	12.9
Gross margin		1.7	1.4	5.5	2.9
Operating income (loss)		$ 1.3	$ 0.3	$ 3.1	$ (5.1)