Valhi Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions		12 Months Ended
	Aug. 10, 2020 $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2021 shares	Jun. 30, 2020 shares	Dec. 31, 2012 shares
Schedule Of Stockholders Equity [Line Items]
Reverse stock split, conversion ratio			0.083
Common stock, par value | $ / shares		$ 0.01	$ 0.01
Treasury stock, shares		1,100,000	1,100,000	1,100,000
Percentage of shares held by majority-owned subsidiary that has to be considered for voting purpose		100.00%
Preferred stock, par value | $ / shares		$ 0.01	$ 0.01
Director Stock Plan
Schedule Of Stockholders Equity [Line Items]
Number of shares authorized						100,000		200,000
Shares awarded under plan		4,000	50,000	50,000
Common stock available for future grant		96,000
Contran
Schedule Of Stockholders Equity [Line Items]
Preferred stock, par value | $ / shares	$ 0.01
Non-cumulative dividend on preferred stock	6.00%
Preferred stock returned to contribution agreement authorized designated	5,000
Series A Preferred Stock
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding					5,000
Preferred stock liquidation preference, per share | $ / shares					$ 133,466.75
Preferred stock, aggregate liquidation preference | $					$ 667.3
Preferred stock, par value | $ / shares					$ 0.01
Non-cumulative dividend on preferred stock					6.00%
NL
Schedule Of Stockholders Equity [Line Items]
Treasury stock, shares			1,200,000
Unrealized gain (loss) on sale of shares attributable to noncontrolling interest | $		$ 3.3	$ (1.7)	$ (0.2)
NL | Director Stock Plan
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		66,150
Kronos Worldwide, Inc.
Schedule Of Stockholders Equity [Line Items]
Shares available for purchase		1,549,110
Treasury stock, shares		100,000
Unrealized gain (loss) on sale of shares attributable to noncontrolling interest | $		$ 3.3	$ (1.7)	$ (0.2)
Kronos Worldwide, Inc. | Director Stock Plan
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		120,200
CompX | Director Stock Plan
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		136,450
Common stock
Schedule Of Stockholders Equity [Line Items]
Shares available for purchase		334,000					833,333