Business Segment Information - Segment Operating Performance (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Net sales	$ 634.6	$ 525.3	$ 1,263.6	$ 1,034.3
Cost of sales	487.9	400.7	946.2	800.4
Gross margin	146.7	124.6	317.4	233.9
Operating income (loss)	71.9	55.6	172.6	106.9
Interest income and other	1.4	1.1	2.3	2.0
Gain on land and related sales		5.6		5.6
Changes in market value of Valhi common stock held by subsidiaries	3.9	0.9	4.0	2.2
Other components of net periodic pension and OPEB expense	(3.3)	(4.6)	(6.6)	(8.9)
General expenses, net	(10.5)	(9.3)	(18.7)	(17.4)
Interest expense	(7.0)	(8.7)	(13.9)	(17.3)
Income before income taxes	56.4	40.6	139.7	73.1
Chemicals
Segment Reporting Information [Line Items]
Net sales	565.3	478.6	1,128.2	943.6
Cost of sales	445.1	369.9	859.0	739.6
Gross margin	120.2	108.7	269.2	204.0
Operating income (loss)	69.2	47.4	155.6	85.1
Component Products
Segment Reporting Information [Line Items]
Net sales	41.6	36.3	83.7	72.2
Cost of sales	28.0	24.9	58.0	49.8
Gross margin	13.6	11.4	25.7	22.4
Operating income (loss)	7.7	5.8	14.0	11.6
Real Estate Management And Development
Segment Reporting Information [Line Items]
Net sales	27.7	10.4	51.7	18.5
Cost of sales	14.8	5.9	29.2	11.0
Gross margin	12.9	4.5	22.5	7.5
Operating income (loss)	$ (5.0)	$ 2.4	$ 3.0	$ 10.2