Name:	nve_Allocationapprovedbyregulators
Namespace Prefix:	nve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

In the quarter ended September 30, 2012, NPC recorded approximately $5.5 million, including an adjustment to previously recorded carrying charges to other income for the remaining balance of the gain on sale.

No definition available.

Name:	nve_Gainrecordedontelecommunicationtowers
Namespace Prefix:	nve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The length of the power purchase agreement under which SPPC will sell energy to CalPeco.

No definition available.

Name:	nve_LengthOfPowerPurchaseAgreement
Namespace Prefix:	nve_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

The number of telecommunications towers sold.

No definition available.

Name:	nve_NumberOfTowersSold
Namespace Prefix:	nve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 40

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.U.Q2)

-URI http://asc.fasb.org/extlink&oid=6955272&loc=d3e221323-122791

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

This element represents the amount of gain (loss) on sale of properties during the reporting period gross of the applicable income taxes realized.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 974

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-15.(a)(1)(ii)

-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 15

-Paragraph a

-Subparagraph 1(ii)

-Article 3

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

- Details

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

Amounts received from the disposal of the long-lived asset during or after the reporting period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2941-110230

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 33, 47

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

The amortization period for recovery of the individual regulatory noncurrent liability in a schedule of regulatory noncurrent liabilities.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 11

-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.