Business Segment Information - Segment Operating Performance (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 475.2	$ 455.2	$ 1,483.5	$ 1,431.4
Cost of sales	376.8	322.5	1,140.0	929.4
Gross margin	98.4	132.7	343.5	502.0
Operating income	41.4	69.2	167.6	318.0
Securities earnings	2.6	19.3	9.0	36.1
Insurance recoveries	0.2	0.5	5.2	0.9
Gain on land sales	4.4		4.4	12.5
Changes in market value of Valhi common stock held by subsidiaries	(3.1)	(7.1)	(0.1)	(11.2)
Other components of net periodic pension and OPEB expense	(4.1)	(3.7)	(12.3)	(11.2)
Litigation settlement expense	0.3		(19.3)	(62.0)
General expenses, net	(9.5)	(7.3)	(28.2)	(32.4)
Interest expense	(10.3)	(14.0)	(30.7)	(45.4)
Income from continuing operations before income taxes	21.9	56.9	95.6	205.3
Chemicals
Segment Reporting Information [Line Items]
Net sales	437.4	410.3	1,358.4	1,312.5
Cost of sales	350.3	291.7	1,053.4	848.3
Gross margin	87.1	118.6	305.0	464.2
Operating income	36.3	61.0	139.6	295.2
Component Products
Segment Reporting Information [Line Items]
Net sales	29.7	30.0	94.6	90.8
Cost of sales	20.2	20.4	64.6	60.5
Gross margin	9.5	9.6	30.0	30.3
Operating income	4.3	4.5	14.3	14.9
Real Estate Management And Development
Segment Reporting Information [Line Items]
Net sales	8.1	14.9	30.5	28.1
Cost of sales	6.3	10.4	22.0	20.6
Gross margin	1.8	4.5	8.5	7.5
Operating income	$ 0.8	$ 3.7	$ 13.7	$ 7.9

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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