Quarterly Results of Operations - Schedule of Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure Quarterly Results Of Operations Schedule Of Quarterly Results Of Operations [Abstract]
Net sales	$ 324.8	$ 383.2	$ 408.8	$ 416.1	$ 432.0	$ 476.5	$ 491.7	$ 462.4	$ 1,532.9	$ 1,862.6	$ 1,863.6
Gross margin	27.5	49.8	56.3	89.3	97.0	115.8	104.2	85.8	222.9	402.8	134.2
Operating income (loss)	(24.9)	(5.0)	(10.1)	34.6	40.5	60.2	46.7	22.8	(5.4)	170.2	(138.7)
Net income (loss)	(35.7)	(13.3)	(139.4)	17.3	13.7	37.5	23.7	4.6	(171.1)	79.5	(126.9)
Amounts attributable to Valhi stockholders:
Net income (loss)	$ (29.9)	$ (11.7)	$ (103.9)	$ 11.9	$ 8.8	$ 28.7	$ 15.5	$ 0.8	$ (133.6)	$ 53.8	$ (98.0)
Basic and diluted income (loss) per share	$ (0.10)	$ (0.03)	$ (0.30)	$ 0.04	$ 0.03	$ 0.08	$ 0.05		$ (0.39)	$ 0.16	$ (0.29)