INVESTMENTS IN SUBSIDIARIES AND OTHER PROPERTY (Details) (USD $)	Dec. 31, 2012		Dec. 31, 2011
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	$ 32,519,000	[1]	$ 29,182,000	[1]
Cash Value-Life Insurance	2,807,000		2,735,000
Non-utility property of NEICO	4,898,000		5,517,000
Property not designated for Utility use	16,083,000		19,235,000
Other non-utility property	353,000		352,000
Total investments and other property	56,660,000		57,021,000
Cash surrender value of life insurance policies	19,900,000		13,500,000
Nevada Power Company [Member]
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	26,383,000	[1]	23,675,000	[1]
Cash Value-Life Insurance	2,807,000		2,735,000
Non-utility property of NEICO	4,898,000		5,517,000
Property not designated for Utility use	15,720,000		18,841,000
Total investments and other property	49,808,000		50,768,000
Sierra Pacific Power Company [Member]
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	6,136,000	[1]	5,507,000	[1]
Property not designated for Utility use	363,000		394,000
Total investments and other property	$ 6,499,000		$ 5,901,000

[1] Rabbi Trust assets represent non-qualified deferred compensation and certain defined benefit plans, which consist of actively traded money market and equity funds with quoted prices in active markets which are considered level 1 in the fair value hierarchy. The balance also includes life insurance policies, which are recorded at the cash surrender value of $19.9 million and $13.5 million at December 31, 2012 and 2011, respectively.