COMMITMENTS AND CONTINGENCIES, Litigation Contingencies and Other Commitments (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Capital Projects
ON Line TUA [Abstract]
Capacity of interconnection (in kV)	500
Utilities' aggregate share in transmission line project (in hundredths)	25.00%
GBT-South's share in the ON Line project (in hundredths)	75.00%
Nevada Power Company [Member]
Royalty claim [Abstract]
Damages sought in DC Lawsuit	$ 600,000,000
Minimum punitive damages sought in DC Lawsuit	1,000,000,000
November 2005 Land Investors [Abstract]
Amount awarded unpaid rent	1,000,000
Amount awarded inverse condemnation and interest	5,100,000
Nevada Power Company [Member] | Capital Projects
ON Line TUA [Abstract]
Capitalized construction costs	370,800,000
Nevada Power Company [Member] | Navajo Generating Station
Royalty claim [Abstract]
Ownership interest in generating stations (in hundredths)	11.30%
Sierra Pacific Power Company
Farad Dam [Abstract]
Number of hydro generating units sold	4
Total capacity of hydro generating units sold (in MW)	10.3
Proceeds from sale of hydro units	8,000,000
Capacity of the Farad Hydro generating unit (in MW)	2.8
Estimate to rebuild diversion dam of the Farad Hydro generating unit	20,000,000
Amount entitled to be recovered for costs incurred to date on Farad Dam	4,000,000
Duration to rebuild the Farad dam from the date of the Court's decision	3 years
ReplacementCost	19,800,000
Sierra Pacific Power Company | Capital Projects
ON Line TUA [Abstract]
Capitalized construction costs	$ 19,400,000