Organization and basis of presentation - Additional Information (Detail)	Mar. 31, 2013
NL [Member]
Schedule Of Significant Accounting Policies [Line Items]
Percentage of ownership held by parent company	87.00%
NL [Member] | Valhi Inc [Member]
Schedule Of Significant Accounting Policies [Line Items]
Percentage of ownership held by parent company	83.00%
Contran Corporation [Member] | Valhi Inc [Member]
Schedule Of Significant Accounting Policies [Line Items]
Percentage of ownership held by parent company	93.00%