Valhi stockholder's equity - Schedule of Common Stock Outstanding (Detail) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012
Schedule Of Stockholders Equity [Line Items]
Shares of common stock, Issued, beginning balance	355.2	355.2
Shares of common stock, Issued, ending balance	355.2	355.2
Shares of common stock, Treasury, beginning balance	(12.2)	(13.2)
Shares of common stock, Treasury, acquired	(1.0)
Shares of common stock, Treasury, ending balance	(13.2)	(13.2)
Shares of common stock, Outstanding, beginning balance	343.0	342.0
Shares of common stock, Outstanding, acquired	(1.0)
Shares of common stock, Outstanding, ending balance	342.0	342.0