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Organization and Basis of Presentation - Additional Information (Detail)
Mar. 31, 2015
Organization And Basis Of Presentation [Line Items]  
Equity method ownership percentage of Kronos Worldwide, Inc 30.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
Valhi Inc  
Organization And Basis Of Presentation [Line Items]  
Equity method ownership percentage of Kronos Worldwide, Inc 83.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= nl_ValhiIncMember
Contran Corporation  
Organization And Basis Of Presentation [Line Items]  
Equity method ownership percentage of Kronos Worldwide, Inc 93.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= nl_ContranCorporationMember
Minimum ownership required to designate board member 5.00%nl_VotingStockOwnershipPercentageRequiredToDesignateBoardMemberUnderVotingAgreement
/ dei_LegalEntityAxis
= nl_ContranCorporationMember