Business and Geographic Segments - Segment Operating Performance (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net sales			$ 2,296.4	$ 1,849.7	$ 1,897.5
Cost of sales			1,716.2	1,437.6	1,462.9
Gross margin			580.2	412.1	434.6
Operating income			318.6	186.1	192.7
Securities earnings			4.0	4.7	11.2
Insurance recoveries			0.1	1.6	7.7
Gain on land sales	$ 10.4	$ 5.6	16.0	0.5	4.4
Gain on sale of business				4.9	3.0
Other components of net periodic pension and OPEB expense			(17.0)	(20.1)	(16.5)
Litigation settlement expense, net					(19.3)
Changes in market value of Valhi common stock held by subsidiaries			3.3	(1.7)	(0.2)
General expenses, net			(34.7)	(34.3)	(37.5)
Interest expense			(32.5)	(36.2)	(40.8)
Income from continuing operations before income taxes			257.8	100.6	104.7
Depreciation and amortization			59.3	68.5	56.8
Capital expenditures			64.1	65.5	59.9
Chemicals
Segment Reporting Information [Line Items]
Net sales			1,939.4	1,638.8	1,731.2
Cost of sales			1,494.5	1,291.0	1,346.8
Gross margin			444.9	347.8	384.4
Operating income			200.8	126.5	160.1
Chemicals | Operating Segment
Segment Reporting Information [Line Items]
Depreciation and amortization			52.8	61.9	50.2
Capital expenditures			58.6	62.8	55.1
Component Products
Segment Reporting Information [Line Items]
Net sales			140.8	114.5	124.2
Cost of sales			98.1	81.7	85.3
Gross margin			42.7	32.8	38.9
Operating income			20.5	11.8	17.8
Component Products | Operating Segment
Segment Reporting Information [Line Items]
Depreciation and amortization			3.8	3.8	3.7
Capital expenditures			4.1	1.7	3.2
Real Estate Management And Development
Segment Reporting Information [Line Items]
Net sales			216.2	96.4	42.1
Cost of sales			123.6	64.9	30.8
Gross margin			92.6	31.5	11.3
Operating income			97.3	47.8	14.8
Real Estate Management And Development | Operating Segment
Segment Reporting Information [Line Items]
Depreciation and amortization			2.7	2.8	2.9
Capital expenditures			$ 1.4	$ 1.0	$ 1.6