Valhi stockholder's equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended						12 Months Ended				12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Series A Preferred Stock [Member]	Dec. 31, 2011 Long Term Incentive Compensation Plan [Member]	Dec. 31, 2010 Long Term Incentive Compensation Plan [Member]	Dec. 31, 2012 Director Plan [Member]	Feb. 28, 2012 Director Plan [Member]	Dec. 31, 2012 NL [Member]	Dec. 31, 2011 NL [Member]	Dec. 31, 2010 NL [Member] Litigation Settlement [Member]	May 31, 2011 Kronos Worldwide, Inc. [Member]	Dec. 31, 2010 Kronos Worldwide, Inc. [Member]	Dec. 31, 2011 Kronos Worldwide, Inc. [Member]	Dec. 31, 2012 Kronos Worldwide, Inc. [Member]	Dec. 31, 2012 CompX [Member]	Dec. 31, 2010 Common stock [Member]
Schedule Of Stockholders Equity [Line Items]
Common stock authorized increased number of shares	500,000,000	500,000,000	500,000,000
Reclassification adjustment from additional paid in capital to common stock through stock split	$ 2.4
Common stock value par or stated value per share	$ 0.01	$ 0.01	$ 0.01
Common stock split proportion	3-for-1												2-for-1
Number of shares authorized to be repurchased																2,000,000		10,000,000
Common stock held by subsidiary, shares		13,200,000	13,200,000	12,200,000						14,400,000	14,400,000			364,000	1,700,000	1,700,000
Additional stock purchased															1,400,000
Aggregate purchase price of shares purchased by subsidiary			8.7	2.0										2.7	12.6
Percentage of shares held by majority-owned subsidiary that has to be considered for voting purpose		100.00%
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	$ 0.01		$ 0.01
Non-cumulative dividend on preferred stock					6.00%
Outstanding stock options						0	0
Number of shares authorized									200,000
Shares awarded under new plan								6,000
Common stock available for future grant								194,000		200,000						200,000	200,000
Equity adjustment attributable to Valhi stockholders												$ 2.1