DIVIDENDS (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2011
Dividend Declaration
Amount (in dollars per share)	$ 0.12	$ 0.12
NPC [Member] \| Declared May 3, 2011 [Member]
Dividend Declaration
Dividend declared to parent company		$ 25,000,000
NPC [Member] \| Declared August 4, 2011 [Member]
Dividend Declaration
Dividend declared to parent company		40,000,000
SPPC [Member] \| Declared May 3, 2011 [Member]
Dividend Declaration
Dividend declared to parent company		12,000,000
SPPC [Member] \| Declared August 4, 2011 [Member]
Dividend Declaration
Dividend declared to parent company		$ 10,000,000
Declared May 3, 2011 [Member]
Dividend Declaration
Declaration Date		May 03, 2011
Payable Date		Jun. 22, 2011
Shareholders of Record Date		Jun. 07, 2011
Declared August 4, 2011 [Member]
Dividend Declaration
Declaration Date		Aug. 04, 2011
Payable Date		Sep. 21, 2011
Shareholders of Record Date		Sep. 06, 2011

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Balance Type:	na
Period Type:	duration

Dividend declared by subsidiary to parent.

+ Details

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Namespace Prefix:	nve
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The day, month, and year (YYYY-MM-DD) that the dividend declared as of or prior to the financial reporting date will be paid in the subsequent period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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- Definition

The day, month and year (YYYY-MM-DD) that the dividend to be paid was declared.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 32
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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- Definition

The date as of when a holder must own the stock to be entitled to the dividend. The ex-dividend date is generally 3 days before the record date.

+ Details

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- Definition

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.

+ Details

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