Quarterly results of operations - Schedule of Quarterly Results of Operations (Detail) (USD $) In Millions, except Per Share data, 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
Net sales	$ 427.4	$ 508.7	$ 568.4	$ 582.8	$ 456.7	$ 568.6	$ 558.9	$ 440.9	$ 2,087.3	$ 2,025.1	$ 1,533.5
Gross margin	55.3	97.4	162.1	260.4	192.9	210.2	197.3	146.3	575.2	746.7	349.2
Operating income	(2.2)	41.1	103.2	203.3	136.5	149.4	139.1	96.4	345.4	521.4	158.3
Net income	9.2	31.8	61.5	119.6	75.8	93.1	72.9	53.2	222.1	295.0	63.8
Amounts attributable to Valhi stockholders
Income (loss) from continuing operations	(12.6)	21.8	43.7	88.5	55.3	71.1	52.2	35.9	141.4	214.5	50.7
Income from discontinued operations	16.1	1.2	0.6	0.5
Net income attributable to Valhi stockholders	3.5	23.0	44.3	89.0	55.6	71.5	52.4	38.0	159.8	217.5	50.3
Earnings per share:
Income (loss) from continuing Operations	$ (0.04)	$ 0.06	$ 0.13	$ 0.26					$ 0.41	$ 0.63	$ 0.14
Income from discontinued operations	$ 0.05	$ 0.01						$ 0.01	$ 0.06	$ 0.01
Net income	$ 0.01	$ 0.07	$ 0.13	$ 0.26	$ 0.16	$ 0.21	$ 0.15	$ 0.11	$ 0.47	$ 0.64	$ 0.14
Net of Noncontrolling Interest [Member]
Amounts attributable to Valhi stockholders
Income from discontinued operations					$ 0.3	$ 0.4	$ 0.2	$ 2.1	$ 18.4	$ 3.0	$ (0.4)
Earnings per share:
Income (loss) from continuing Operations					$ 0.16	$ 0.21	$ 0.15	$ 0.10