Valhi stockholder's equity - Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income Loss [Line Items]
Marketable securities, Balance at beginning of year	$ 6.4	$ 14.6	$ 9.0
Balance at beginning of year	(23.3)	21.2	(3.2)
Marketable securities, Unrealized gain (loss) arising during the year	4.1	(8.2)	5.6
Other comprehensive income (loss)	(18.7)	(44.5)	4.6
Common stock sale	(8.4)
Marketable securities, Balance at end of year	2.1	6.4	14.6
Currency translation, Balance at beginning of year	37.5	59.2	50.3
Currency translation, Arising during the year	23.0	(21.7)	(0.1)
Currency translation, Common stock sale	(7.2)
Currency translation, Balance at end of year	53.3	37.5	59.2
Balance at end of year	(42.0)	(23.3)	21.2
Pension Plan Defined Benefit [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	(72.6)	(59.8)
Balance at beginning of year	(72.6)	(59.8)	(66.1)
Amortization of prior service cost and net losses included in net periodic pension cost	6.1	4.0	4.2
Net actuarial loss arising during year	(35.0)	(16.8)	(6.5)
Plan amendment			(2.0)
Balance at end of year	(101.5)	(72.6)	(59.8)
OPEB [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of year	5.4	7.2	3.6
Amortization of prior service cost and net losses included in net periodic pension cost	(1.0)	(0.5)	(0.4)
Net actuarial loss arising during year	(0.3)	(1.3)	(1.3)
Plan amendment			5.1
Balance at end of year	4.1	5.4	7.2
Kronos Worldwide, Inc. [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Common stock sale			19.8
Currency translation, Common stock sale			9.0
Kronos Worldwide, Inc. [Member] | Pension Plan Defined Benefit [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Common stock sale			10.6
Kronos Worldwide, Inc. [Member] | OPEB [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Common stock sale			$ 0.2