Gain loss related to real estate litigation settlement.

No definition available.

Name:	nl_GainLossRelatedToRealEstateLitigationSettlement
Namespace Prefix:	nl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Litigation matter cases in which company not been found liable numbers.

+ References

No definition available.

+ Details

Name:	nl_LitigationMatterCasesInWhichCompanyNotBeenFoundLiableNumbers
Namespace Prefix:	nl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Litigation matter cases in which company not been found liable period.

+ References

No definition available.

+ Details

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Namespace Prefix:	nl_
Data Type:	xbrli:durationItemType
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- Definition

Number of environmental sites with no estimate.

+ References

No definition available.

+ Details

Name:	nl_NumberOfEnvironmentalSitesWithNoEstimate
Namespace Prefix:	nl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of plaintiffs have been administratively dismissed or placed on inactive docket.

+ References

No definition available.

+ Details

Name:	nl_NumberOfPlaintiffsHaveBeenAdministrativelyDismissedOrPlacedOnInactiveDocket
Namespace Prefix:	nl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of plaintiffs involved.

+ References

No definition available.

+ Details

Name:	nl_NumberOfPlaintiffsInvolved
Namespace Prefix:	nl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of sites associated to accrual for environmental remediation.

+ References

No definition available.

+ Details

Name:	nl_NumberOfSitesAssociatedToAccrualForEnvironmentalRemediation
Namespace Prefix:	nl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The net proceeds or assets obtained in excess of (less than) the net carrying amount of assets recorded, or assets distributed and liabilities assumed less than (in excess of) estimated litigation liability extinguished, in settlement of a litigation matter. Represents (for other than an insurance entity in its normal claims settlement process), the amount of income (expense) recognized in the period to settle pending or threatened litigation and insurance claims.

+ References

No definition available.

+ Details

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Namespace Prefix:	nl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Upper range of environmental loss estimate.

+ References

No definition available.

+ Details

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Namespace Prefix:	nl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Present value of the accrual for environmental loss contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 161, 132

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q1)

-URI http://asc.fasb.org/extlink&oid=6572457&loc=d3e149879-122751

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 1

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The number of claims settled and dismissed during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9, 10, 11, 12

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received for the settlement of litigation during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3536-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of known and reasonably estimable amounts of recoveries from third-parties pertaining to an entity's environmental remediation obligations. An entity's balance sheet may include several assets that relate to an environmental remediation obligation. Among them are the following: a. Receivables from other potentially responsible parties that are not providing initial funding; b. anticipated recoveries from insurers; and c. anticipated recoveries from prior owners as a result of indemnification agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6393211&loc=d3e13022-110858

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 161

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Period Type:	instant

Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended	9 Months Ended
	May 31, 2012	Jun. 30, 2012	Sep. 30, 2012 Plaintiff Cases site	Dec. 31, 2011
Liable cases			100
Liable periods			20 years
Receivables recognized for recoveries			$ 0	$ 0
Accrued environmental obligations approximately			49
Sites associated with remediation			50
Remediation and related matters possible to estimate costs			79
Currently not able to estimate a range of costs to sites			5
Proceeds from legal settlements			7.5
Number of cases pending			1,125
Number of Plaintiffs Involved in Pending Cases			1,995
Number of cases administratively dismissed or inactive			8,075
Aggregate cash received under settlement agreement	15.6
Pre-tax gain recognized on real estate property		$ 15