REGULATORY ACTIONS, Deferred Energy (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Nevada Deferred Energy
Nevada Deferred Energy Balance at period end	$ 17,284
Amortization	94,134
Cumulative balance as filed	(151,880)
Deferred Energy Under Collection	75,030	[1]
Reinstatement of deferred energy (effective 6/07, 10 years)	95,103
Total Deferred Energy	112,387
Deferred Assets
Deferred energy	81,274		87,072
Deferred Energy Electric Current	30,122		0
Deferred Energy Gas Current	991		0
Current Liabilities
Deferred energy	0		136,865
NPC Electric [Member]
Nevada Deferred Energy
Nevada Deferred Energy Balance at period end	12,395
Amortization	57,887
Cumulative balance as filed	(101,117)
Deferred Energy Under Collection	55,625	[1]
Reinstatement of deferred energy (effective 6/07, 10 years)	95,103
Total Deferred Energy	107,498
Deferred Assets
Deferred energy	80,109
Deferred Energy Electric Current	27,389
SPPC Electric [Member]
Nevada Deferred Energy
Nevada Deferred Energy Balance at period end	2,733
Amortization	19,196
Cumulative balance as filed	(32,693)
Deferred Energy Under Collection	16,230	[1]
Reinstatement of deferred energy (effective 6/07, 10 years)	0
Total Deferred Energy	2,733
Deferred Assets
Deferred Energy Electric Current	2,733
SPPC Gas [Member]
Nevada Deferred Energy
Nevada Deferred Energy Balance at period end	2,156
Amortization	17,051
Cumulative balance as filed	(18,070)
Deferred Energy Under Collection	3,175	[1]
Reinstatement of deferred energy (effective 6/07, 10 years)	0
Total Deferred Energy	2,156
Deferred Assets
Deferred energy	1,165
Deferred Energy Gas Current	$ 991

[1] These deferred energy under collections are subject to quarterly rate resets as discussed in Note 1, Summary of Significant AccountingPolicies, Deferred Energy Accounting, of the Notes to Financial Statements in the 2012 Form 10-K.