Valhi stockholder's equity - Reconciliation of Numerator Used in Calculation of Earnings (Loss) Per Share (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Income from continuing operations attributable to Valhi stockholders	$ (12.6)	$ 21.8	$ 43.7	$ 88.5	$ 55.3	$ 71.1	$ 52.2	$ 35.9	$ 141.4	$ 214.5	$ 50.7
Adjusted income from continuing operations attributable to Valhi stockholders									141.4	214.5	48.6
NL [Member] | Litigation Settlement [Member]
Calculation Of Numerator And Denominator In Earnings Per Share [Line Items]
Equity adjustment											$ (2.1)