Name:	nvl_EffectiveIncomeTaxRateReconciliationAtCanadianStatutoryIncomeTaxRate
Namespace Prefix:	nvl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateChangeInDeferredTaxAssetsValuationAllowance
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations attributable to the deduction for dividends paid or received under enacted tax laws.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateDeductionsDividends
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the year/accounting period and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations, that is attributable to exchange remeasurement of deferred income taxes.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateExchangeRemeasurementOfDeferredIncomeTaxes
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateExchangeTranslationAdjustments
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations attributable to nondeductible expenses under enacted tax laws.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateNondeductibleExpense
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The sum of the differences between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations attributable to changes in all income tax contingencies, whether recorded or adjusted, during the period.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateTaxContingencies
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The sum of the differences between the effective income tax rate and Canadian statutory income tax rate that can be explained by all tax credits generated or utilized under enacted tax laws during the period and other allowances.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateTaxCreditsAndOtherAllowances
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryIncomeTaxRateTaxRateDifferencesOnForeignEarnings
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the Canadian statutory income tax rates to pretax income from continuing operations, that is attributable to changes in the income tax rates under enacted tax laws in the period.

No definition available.

Name:	nvl_IncomeTaxReconciliationCanadianStatutoryRateChangeInEnactedTaxRate
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of income tax expense or benefit for the period computed by applying the Canadian statutory tax rates to pretax income from continuing operations.

No definition available.

Name:	nvl_IncomeTaxReconciliationIncomeTaxExpenseBenefitAtCanadianStatutoryIncomeTaxRate
Namespace Prefix:	nvl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	nvl_IncreaseDecreaseForTaxesOnIncomeLossAbstract
Namespace Prefix:	nvl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 6.I.7)

-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Current Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6509736

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section I

-Subsection 7

Name:	us-gaap_CurrentStateAndLocalTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32687-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(2))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 2

-Article 4

Name:	us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

Name:	us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Article 4

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Income Tax Expense (or Benefit)

-URI http://asc.fasb.org/extlink&oid=6515339

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Name:	us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

Name:	us-gaap_IncomeTaxReconciliationOtherAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense (benefit).

Name:	us-gaap_IncomeTaxReconciliationPriorYearIncomeTaxes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.