REGULATORY ACTIONS, Deferred Energy (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Nevada Deferred Energy
Cumulative balance authorized in DEAA	$ (152,990)
Amortization	111,977
Deferred Energy Under Collection	118,397	[1]
Nevada Deferred Energy Balance at period end	77,384
Reinstatement of deferred energy (effective 6/07, 10 years)	89,906
Total Deferred Energy	167,290
Deferred Assets
Deferred energy costs current	82,235		0
Deferred Energy Costs Non Current	85,055		87,072
Liabilities, Current [Abstract]
Deferred energy	0		136,865
NPC Electric
Nevada Deferred Energy
Cumulative balance authorized in DEAA	(102,227)
Amortization	69,288
Deferred Energy Under Collection	95,465	[1]
Nevada Deferred Energy Balance at period end	62,526
Reinstatement of deferred energy (effective 6/07, 10 years)	89,906
Total Deferred Energy	152,432
Deferred Assets
Deferred energy costs current	68,391
Deferred Energy Costs Non Current	84,041
SPPC Electric
Nevada Deferred Energy
Cumulative balance authorized in DEAA	(32,693)
Amortization	23,695
Deferred Energy Under Collection	19,697	[1]
Nevada Deferred Energy Balance at period end	10,699
Reinstatement of deferred energy (effective 6/07, 10 years)	0
Total Deferred Energy	10,699
Deferred Assets
Deferred Energy Electric Current	10,322
Deferred Energy Costs Non Current	377
SPPC Gas
Nevada Deferred Energy
Cumulative balance authorized in DEAA	(18,070)
Amortization	18,994
Deferred Energy Under Collection	3,235	[1]
Nevada Deferred Energy Balance at period end	4,159
Reinstatement of deferred energy (effective 6/07, 10 years)	0
Total Deferred Energy	4,159
Deferred Assets
Deferred Energy Gas Current	3,522
Deferred Energy Costs Gas Non Current	$ 637

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