Business Segment Information - Segment Operating Performance (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Net sales	$ 629.0	$ 509.0
Cost of sales	458.3	399.7
Gross margin	170.7	109.3
Operating income	100.7	51.3
Securities earnings	0.9	0.9
Interest income and other	0.9	0.9
Other components of net periodic pension and OPEB expense	(3.3)	(4.3)
Changes in market value of Valhi common stock held by subsidiaries	0.1	1.3
General expenses, net	(8.2)	(8.1)
Interest expense	(6.9)	(8.6)
Income before income taxes	83.3	32.5
Chemicals
Segment Reporting Information [Line Items]
Net sales	562.9	465.0
Cost of sales	413.9	369.7
Gross margin	149.0	95.3
Operating income	86.4	37.7
Component Products
Segment Reporting Information [Line Items]
Net sales	42.1	35.9
Cost of sales	30.0	24.9
Gross margin	12.1	11.0
Operating income	6.3	5.8
Real Estate Management And Development
Segment Reporting Information [Line Items]
Net sales	24.0	8.1
Cost of sales	14.4	5.1
Gross margin	9.6	3.0
Operating income	$ 8.0	$ 7.8