Valhi Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	May 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 28, 2012
Schedule Of Stockholders Equity [Line Items]
Common stock, shares authorized	500,000,000	500,000,000	500,000,000
Common stock split proportion	3-for-1
Treasury stock, shares		13,200,000	13,200,000	13,200,000
Percentage of shares held by majority-owned subsidiary that has to be considered for voting purpose		100.00%
Preferred stock, par value		$ 0.01	0.01
Series A Preferred Stock
Schedule Of Stockholders Equity [Line Items]
Preferred stock, shares outstanding		5,000
Preferred stock liquidation preference, per share		$ 133,466.75
Preferred stock, aggregate liquidation preference		$ 667.3
Preferred stock, par value		$ 0.01
Non-cumulative dividend on preferred stock		6.00%
NL
Schedule Of Stockholders Equity [Line Items]
Treasury stock, shares		14,400,000	14,400,000
Kronos Worldwide, Inc.
Schedule Of Stockholders Equity [Line Items]
Shares available for purchase		1,950,000
Treasury stock, shares		1,700,000	1,700,000
Common stock
Schedule Of Stockholders Equity [Line Items]
Shares available for purchase					10,000,000
Long Term Incentive Compensation Plan
Schedule Of Stockholders Equity [Line Items]
Outstanding stock options		0	0
Director Plan
Schedule Of Stockholders Equity [Line Items]
Number of shares authorized						200,000
Shares awarded under new plan		12,000	5,000	6,000
Common stock available for future grant		177,000
Director Plan | NL
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		185,000
Director Plan | Kronos Worldwide, Inc.
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		185,000
Director Plan | CompX
Schedule Of Stockholders Equity [Line Items]
Common stock available for future grant		185,000