JOINTLY OWNED FACILITIES (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 MW	Dec. 31, 2013	Dec. 31, 2011
Nevada Power Company [Member]
Jointly Owned Utility Plant Interests [Line Items]
Plant in Service	$ 685,766		$ 689,275
Accumulated Depreciation	303,481		296,446
Net Plant in Service	382,285		392,829
CWIP	17,100		8,920
Nevada Power Company [Member] | Navajo Generating Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
% Owned (in hundredths)	11.30%		11.30%
Plant in Service	253,711		270,448
Accumulated Depreciation	149,969		148,582
Net Plant in Service	103,742		121,866
CWIP	5,601		1,117
Nevada Power Company [Member] | Reid Gardner Generating Station No. 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
% Owned (in hundredths)	32.20%		32.20%
Plant in Service	184,474		171,485
Accumulated Depreciation	100,277		97,042
Net Plant in Service	84,197		74,443
CWIP	9,141		7,600
Proportionate share of base load capacity (in megawatts)	25
Proportionate share of peaking capacity (in megawatts)	232
ContractExpirationDate	June 2013
Ownership percentage of Reid Gardner		100.00%
Nevada Power Company [Member] | Silverhawk Generating Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
% Owned (in hundredths)	75.00%		75.00%
Plant in Service	247,581		247,342
Accumulated Depreciation	53,235		50,822
Net Plant in Service	194,346		196,520
CWIP	2,358		203
Sierra Pacific Power Company [Member] | Valmy Generating Station [Member]
Jointly Owned Utility Plant Interests [Line Items]
% Owned (in hundredths)	50.00%		50.00%
Plant in Service	336,038		331,753
Accumulated Depreciation	214,335		215,642
Net Plant in Service	121,703		116,111
CWIP	$ 10,808		$ 6,682
California Water Resources Department [Member] | Jointly Owned Electricity Generation Plant [Member] | Reid Gardner Generating Station No. 4 [Member]
Jointly Owned Utility Plant Interests [Line Items]
% Owned (in hundredths)	67.80%