Name:	nvl_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisable
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Weighted average price of equity instruments other than options that were either forfeited or expired.

No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the share-based compensation plan.

No definition available.

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Exercise Price

No definition available.

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Weighted average price at which instrument holders acquired shares when converting their equity instruments (other than options) into shares.

No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

No definition available.

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Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Aggregate Intrinsic Value, Exercised

No definition available.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of non-option equity instruments exercised by participants.

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Number of shares under non-option equity instrument agreements that were either cancelled or expired.

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Net number of non-option equity instruments granted to participants.

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Data Type:	xbrli:sharesItemType
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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Data Type:	xbrli:stringItemType
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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

The combined weighted average of the accumulated differences between the fair values on underlying shares and exercises prices to acquire such shares as of the grant date on options that were either forfeited or lapsed.

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Data Type:	num:perShareItemType
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Period Type:	duration

The grant-date intrinsic value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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

Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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Data Type:	xbrli:stringItemType
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Period Type:	duration

Intrinsic value of equity-based compensation awards outstanding. Excludes stock and unit options.

No definition available.

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

Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.