Name:	neu_AccrualForEnvironmentalDismantlingAndDecommissioning
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Present value of the accrual for environmental loss contingencies at an individual site as of the balance sheet date (if the accrual qualifies for discounting) excluding costs for dismantling and decontamination.

No definition available.

Name:	neu_AccrualForEnvironmentalRemediation
Namespace Prefix:	neu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The component of the environmental loss contingency accrual that is specifically related to remediation of groundwater and soil.

No definition available.

Name:	neu_AccrualForEnvironmentalRemediationOfGroundWaterAndSoil
Namespace Prefix:	neu_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: 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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 161

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6952336&loc=d3e14326-108349

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Undiscounted amount of the accrual for environmental loss contingencies maturing after the fifth fiscal year following the latest fiscal year.

Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 1

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Undiscounted amount of the accrual for environmental loss contingencies maturing in the fifth fiscal year following the latest fiscal year.

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Namespace Prefix:	us-gaap_
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Undiscounted amount of the accrual for environmental loss contingencies maturing in the fourth fiscal year following the latest fiscal year.

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Namespace Prefix:	us-gaap_
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Undiscounted amount of the accrual for environmental loss contingencies maturing in the second fiscal year following the latest fiscal year.

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Namespace Prefix:	us-gaap_
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Undiscounted amount of the accrual for environmental loss contingencies maturing in the third fiscal year following the latest fiscal year.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Undiscounted amount of the accrual for environmental loss contingencies maturing in the next fiscal year following the latest fiscal year.

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Rate applied to the undiscounted amount of environmental loss contingencies at an individual site to arrive at the present value recorded as of the balance sheet date.

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 132, 161, 163

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Present value of the accrual for environmental loss contingencies at an individual site as of the balance sheet date (if the accrual qualifies for discounting).

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 AICPA

-Name Statement of Position (SOP)

-Number 96-1

-Paragraph 132, 161, 163

-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.

Name:	us-gaap_SiteContingencyAccrualPresentValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Estimated undiscounted amount of the accrual for the environmental loss contingencies at an individual site as of the balance sheet date.