CONSOLIDATED INCOME STATEMENTS (Unaudited) Parenthetical (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt:)	$ 2,835	$ 5,926	$ 9,045	$ 10,864
Nevada Power Company [Member]
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt:)	2,330	5,444	8,120	9,976
Sierra Pacific Power Company [Member]
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt:)	$ 505	$ 482	$ 925	$ 888

The component of the allowance for funds used during construction during the period comprised of interest on borrowed funds used in financing the construction of regulated assets, which may be reflected as a reduction of interest expense.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 71
-Paragraph 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 980
-SubTopic 835
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Name:	us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration