Long-term debt - Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Long-term debt
Total debt	$ 800.2	$ 910.1
Less current maturities	29.6	29.6
Total long-term debt	770.6	880.5
Other Subsidiary Debt [Member]
Long-term debt
Other	9.8	9.2
Subsidiary Debt [Member]
Long-term debt
Total subsidiary debt	401.2	502.5
VALHI, INC. [Member]
Long-term debt
Total Valhi debt	399.0	407.6
VALHI, INC. [Member] | Contran [Member]
Long-term debt
Debt instrument	149.0	157.6
VALHI, INC. [Member] | Notes Payable, Other Payables [Member] | Snake River [Member]
Long-term debt
Debt instrument	250.0	250.0
Kronos Worldwide, Inc. [Member]
Long-term debt
Debt instrument	98.6	384.5
Revolving European credit facility	12.8	13.2
Kronos Worldwide, Inc. [Member] | Contran [Member]
Long-term debt
Promissory note	185.0
CompX [Member] | Timet Finance Management Company [Member]
Long-term debt
Debt instrument	18.2	18.5
WCS [Member]
Long-term debt
Financing capital lease	69.6	69.9
WCS [Member] | Promissory Notes [Member]
Long-term debt
Promissory note	$ 7.2	$ 7.2