REGULATORY ACTIONS, Deferred Energy (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Nevada Deferred Energy
Cumulative Balance authorized in DEAA	$ 334,102		$ 220,064	[1]
Amortization	247,489		74,215
Deferred Energy Over Collections	173,466	[2]	184,776	[3]
Nevada Deferred Energy Balance at period end - Subtotal	(260,079)		(330,625)
Cumulative CPUC balance			(3,210)	[4]
Reinstatement of deferred energy (effective 6/07, 10 years)	117,440		132,409
Total Deferred Energy	(142,639)		(201,426)
Deferred Assets
Deferred energy	102,525		117,623
Current Liabilities
Deferred energy	(245,164)		(315,839)
Liabilities held for sale			3,210
NPC Electric [Member]
Nevada Deferred Energy
Cumulative Balance authorized in DEAA	189,032	[5]	102,398	[1],[6]
Amortization	120,340		22,441
Deferred Energy Over Collections	106,022	[2]	106,178	[3]
Nevada Deferred Energy Balance at period end - Subtotal	(174,714)		(186,135)
Reinstatement of deferred energy (effective 6/07, 10 years)	117,440		132,409
Total Deferred Energy	(57,274)		(53,726)
SPPC Electric [Member]
Nevada Deferred Energy
Cumulative Balance authorized in DEAA	115,955		100,625	[1]
Amortization	104,909		40,682
Deferred Energy Over Collections	45,291	[2]	55,615	[3]
Nevada Deferred Energy Balance at period end - Subtotal	(56,337)		(115,558)
Cumulative CPUC balance			(3,210)	[4]
Total Deferred Energy	(56,337)		(118,768)
Current Liabilities
Deferred energy	56,337		115,558
Liabilities held for sale			3,210
SPPC Gas [Member]
Nevada Deferred Energy
Cumulative Balance authorized in DEAA	29,115		17,041	[1]
Amortization	22,240		11,092
Deferred Energy Over Collections	22,153	[2]	22,983	[3]
Nevada Deferred Energy Balance at period end - Subtotal	(29,028)		(28,932)
Total Deferred Energy	(29,028)		(28,932)
Current Liabilities
Deferred energy	$ 29,028		$ 28,932

[1] These deferred costs include PUCN ordered adjustments.

[2] These deferred energy over collections will be filed in the March 2012 DEAA filings

[3] These deferred over collections were requested in March 2011 DEAA filings.

[4] Refer to Note 16, Assets Held For Sale

[5] Refer to NPC 2011 DEAA “Settled Regulatory Actions” below for separate discussion regarding rate offset of this balance.

[6] Refer to NPC DEAA under “Settled Regulatory Actions” below for separate discussion regarding the NPC rate offset of their 2010 cumulative balance against their deferred rate increase included in other regulatory assets.