REGULATORY ACTIONS, Summary of Regulatory Actions (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Nevada Power Company [Member]
Declatory Order [Abstract]
Amount Of gain approved by PUCN	$ 27.3
Gain on Sale of Telecommunications Towers	32.0
Gain Recorded On Telecommunication Towers	5.5
Revenue Requirement Subject To Change:
Authorized/Requested Revenue Requirement	127.6
Present Revenue Requirement	126.6
$ Change in Revenue Requirement	1.0
DEAA Filings [Abstract]
Overall increase South	37.7
FERC Matters [Abstract]
FERC Transmission Rate Case	11.3
Ferc Effective Date	January 1, 2013
Nevada Power Company [Member] | DEAA [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012	[1]
Authorized/Requested Revenue Requirement	11.5	[1]
Present Revenue Requirement	0	[1]
$ Change in Revenue Requirement	11.5	[1]
Nevada Power Company [Member] | REPR [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012	[2]
Authorized/Requested Revenue Requirement	37.4	[2]
Present Revenue Requirement	8.5	[2]
$ Change in Revenue Requirement	28.9	[2]
Nevada Power Company [Member] | TRED [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012	[2]
Authorized/Requested Revenue Requirement	15.3	[2]
Present Revenue Requirement	18.0	[2]
$ Change in Revenue Requirement	(2.7)	[2]
Nevada Power Company [Member] | EEPR Base [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013	[2]
Authorized/Requested Revenue Requirement	33.1	[2]
Present Revenue Requirement	57.3	[2]
$ Change in Revenue Requirement	(24.2)	[2]
Nevada Power Company [Member] | EEPR Amortization [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013	[2]
Authorized/Requested Revenue Requirement	8.9	[2]
Present Revenue Requirement	21.2	[2]
$ Change in Revenue Requirement	(12.3)	[2]
Nevada Power Company [Member] | EEIR Base [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	11.0
Present Revenue Requirement	16.8
$ Change in Revenue Requirement	(5.8)
Nevada Power Company [Member] | EEIR Amortization [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	10.4
Present Revenue Requirement	4.8
$ Change in Revenue Requirement	5.6
Sierra Pacific Power Company [Member]
FERC Matters [Abstract]
FERC Transmission Rate Case	3.2
Ferc Effective Date	January 1, 2013
Sierra Pacific Power Company [Member] | SPPC Gas [Member]
DEAA Filings [Abstract]
Overall Increase North	0.2
Sierra Pacific Power Company [Member] | SPPC Electric [Member]
Revenue Requirement Subject To Change:
Authorized/Requested Revenue Requirement	63.3
Present Revenue Requirement	65.8
$ Change in Revenue Requirement	(2.5)
DEAA Filings [Abstract]
Overall Increase North	1.7
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | REPR [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Authorized/Requested Revenue Requirement	43.3
Present Revenue Requirement	38.5
$ Change in Revenue Requirement	4.8
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | TRED [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Authorized/Requested Revenue Requirement	6.1
Present Revenue Requirement	9.2
$ Change in Revenue Requirement	(3.1)
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | EEPR Base [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	5.4
Present Revenue Requirement	9.8
$ Change in Revenue Requirement	(4.4)
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | EEPR Amortization [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	1.7
Present Revenue Requirement	4.7
$ Change in Revenue Requirement	(3.0)
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | EEIR Base [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	4.9
Present Revenue Requirement	3.1
$ Change in Revenue Requirement	1.8
Sierra Pacific Power Company [Member] | SPPC Electric [Member] | EEIR Amortization [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Jan. 2013
Authorized/Requested Revenue Requirement	1.9
Present Revenue Requirement	0.5
$ Change in Revenue Requirement	$ 1.4

[1] This rate request represents revenues previously recorded as a result of NPC's 2008 GRC. As such, NPC will not record furtherrevenue related to this rate component, but will collect such amounts from its customers. Reference Note 3,Regulatory Actions, NPC 2008 GRC, of the Notes to Financial Statements in the 2011 Form 10-K.

[2] Represents programs that require the Utilities to collect funds from customers for which the related costs are equal to the revenues collected.As a result, such programs have no effect on Operating or Net Income.