Name:	np_DefinedBenefitPlanPensionPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAbstract
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Represents the aggregate pension accumulated benefit obligation for pension plans with plan assets in excess of accumulated benefit obligations as of the measurement date of each statement of financial position presented, if aggregate disclosures are presented.

No definition available.

Name:	np_DefinedBenefitPlanPensionPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAggregateAccumulatedBenefitObligation
Namespace Prefix:	np_
Data Type:	xbrli:monetaryItemType
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Represents the aggregate fair value of plan assets for pension plans with plan assets in excess of accumulated benefit obligations as of the measurement date of each statement of financial position presented, if aggregate disclosures are presented.

No definition available.

Name:	np_DefinedBenefitPlanPensionPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAggregateFairValueOfPlanAssets
Namespace Prefix:	np_
Data Type:	xbrli:monetaryItemType
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Represents the aggregate projected benefit obligation for pension plans with plan assets in excess of accumulated benefit obligations as of the measurement date of each statement of financial position presented, if aggregate disclosures are presented.

No definition available.

Name:	np_DefinedBenefitPlanPensionPlansWithPlanAssetsInExcessOfAccumulatedBenefitObligationsAggregateProjectedBenefitObligation
Namespace Prefix:	np_
Data Type:	xbrli:monetaryItemType
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Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Period Type:	instant

Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (j)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

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Amount, after tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
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Period Type:	instant

- References

No definition available.

Name:	us-gaap_DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAbstract
Namespace Prefix:	us-gaap_
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Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

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Namespace Prefix:	us-gaap_
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Fair value of plan assets for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

Name:	us-gaap_DefinedBenefitPlanPensionPlansWithAccumulatedBenefitObligationsInExcessOfPlanAssetsAggregateFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921