MERGER RELATED ACTIVITIES (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Merger Related Activities [Line Items]
Merger related costs	$ 7,857,000	$ 0	$ 21,409,000	$ 0
Nevada Power Company
Merger Related Activities [Line Items]
Merger related costs	5,620,000	0	14,487,000	0
Sierra Pacific Power Company
Merger Related Activities [Line Items]
Merger related costs	2,008,000	0	5,528,000	0
MidAmerican Merger
Merger Related Activities [Line Items]
Merger Agreement Date			May 29, 2013
Expected Merger Closing Date			in late 2013 or first quarter of 2014
Merger Closing Conditions			the approval of the MidAmerican Merger Agreement by the holders of a majority of the outstanding shares of NVE common stock. On September 25, 2013, NVE’s stockholders approved the MidAmerican Merger Agreement. Consequently, this closing condition has been satisfied; the receipt of regulatory approvals and other consents required to consummate the MidAmerican Merger, including, among others, approvals from the PUCN and the FERC on terms and conditions specified in the MidAmerican Merger Agreement (in July 2013, filings were made with the PUCN and FERC. See Note 4, Regulatory Actions, for further details of these filings); the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. On July 22, 2013, NVE was advised that the Department of Justice and the U.S. Federal Trade Commission had terminated the applicable waiting period under the Hart-Scott-Rodino Act.  Consequently, the closing condition with respect to the Hart-Scott-Rodino Act has been satisfied; the absence of the occurrence of a company material adverse effect (as defined in the MidAmerican Merger Agreement) after the date of the MidAmerican Merger Agreement; and other customary closing conditions.
Merger Termination Right			The MidAmerican Merger Agreement contains certain termination rights and fees for both NVE and MEHC. In the event of termination of the MidAmerican Merger under certain circumstances, NVE may be obligated to pay MEHC a termination fee of up to $169.7 million.
Merger Termination Fee	169,700,000		169,700,000
Merger Share Exchange Ratio			$ 23.75
Shareholder approval date	September 25, 2013		September 25, 2013
Filing Date of PUCN filing			July 2013
Filing Date of FERC filing			July 2013
Satisfaction date of Hart Scott Rodino Condition			July 22, 2013
Change of Control Description of Debt			As a result, NVE, NPC and SPPC will be required to offer to purchase approximately $315.0 million, $3.1 billion, and $951.7 million, respectively, of debt at 101% of par within 10 days after the MidAmerican Merger closing.
Merger Restrictions			The MidAmerican Merger Agreement contains customary representations, warranties and covenants for both NVE and MEHC. These covenants include an obligation for us, subject to certain exceptions, to conduct our business in a manner substantially consistent with our current practice. In addition, the covenants contain several restrictions that apply unless MEHC’s consent is received, including limitations on making certain business acquisitions, limitations on our total capital spending, limitations on the extent to which we may obtain financing through long-term debt or equity issuances and limitations on increasing our common stock dividend payout.
Merger Description			On May 29, 2013, NVE entered into the MidAmerican Merger Agreement.  The MidAmerican Merger Agreement provides for the merger of Silver Merger Sub, Inc. with and into NVE, with NVE continuing as the surviving corporation.  Once merged, NVE will become an indirect wholly owned subsidiary of MEHC.  The closing is expected to occur in late 2013 or during the first quarter of 2014.
MidAmerican Merger | Parent Company
Merger Related Activities [Line Items]
Debt required to be tendered	315,000,000		315,000,000
Average interest rate of debt required to be tendered			6.25%
MidAmerican Merger | Nevada Power Company
Merger Related Activities [Line Items]
Debt required to be tendered	3,100,000,000		3,100,000,000
Average interest rate of debt required to be tendered			6.42%
MidAmerican Merger | Sierra Pacific Power Company
Merger Related Activities [Line Items]
Debt required to be tendered	$ 951,700,000		$ 951,700,000
Average interest rate of debt required to be tendered			5.51%
One Company Merger | Nevada Power Company
Merger Related Activities [Line Items]
Merger Description			NPC and SPPC filed a joint application with the PUCN to merge SPPC into NPC (“One Company Merger”) and to call the surviving entity NVEOC. The One Company Merger is subject to approval by the PUCN and FERC.
One Company Merger | Sierra Pacific Power Company
Merger Related Activities [Line Items]
Merger Description			NPC and SPPC filed a joint application with the PUCN to merge SPPC into NPC (“One Company Merger”) and to call the surviving entity NVEOC. The One Company Merger is subject to approval by the PUCN and FERC.