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Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Income Tax Disclosure [Abstract]
Tax Reassessment Cash Liability	$ 15.7

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- Definition

Cash tax liability would be recognized had proposed adjustment were ultimately to be assessed.

+ References

No definition available.

+ Details

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Namespace Prefix:	nl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- Details

Name:	us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration