CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
OPERATING REVENUES:
OPERATING REVENUES	$ 2,979,177		$ 2,943,307		$ 3,280,222
Operating Expenses
Fuel for power generation	565,381		680,585		821,484
Purchased power	603,999		633,874		648,881
Gas purchased for resale	74,352		125,155		137,702
Deferred energy	(106,728)		(83,333)		113,107
Energy efficiency program costs	96,677		43,537		0
Other operating expenses	412,372		411,115		414,241
Maintenance	109,725		103,307		104,567
Depreciation and amortization	377,640		357,937		333,059
Taxes other than income	60,696		60,465		62,746
Total Operating Expenses	2,194,114		2,332,642		2,635,787
OPERATING INCOME	785,063		610,665		644,435
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt)	(299,484)		(328,710)		(333,010)
Interest income (expense) on regulatory items	(7,721)		(4,115)		(3,695)
AFUDC - equity	9,146		10,873		28,112
Other income	24,299		10,558		28,019
Other expense	(22,765)		(48,924)		(23,113)
Total Other Income (Expense)	(296,525)		(360,318)		(303,687)
Income Before Income Tax Expense	488,538		250,347		340,748
Income Tax Expense (Benefit)	166,592		86,915		113,764
NET INCOME	321,946		163,432		226,984
Other comprehensive income (loss):
Change in compensation retirement benefits liability and amortization	1,598		357		403
Change in market value of risk management assets and liabilities	(539)		(686)		0
OTHER COMPREHENSIVE INCOME(LOSS)	(2,137)		(1,043)		(403)
COMPREHENSIVE INCOME	319,809		162,389		226,581
Amount per share basic and diluted - (Note 15)
Net income per share - basic	$ 1.37		$ 0.69		$ 0.97
Net income per share - diluted	$ 1.35		$ 0.69		$ 0.96
Weighted Average Shares of Common Stock Outstanding - basic	235,840,558		235,847,596		235,048,347
Weighted Average Shares of Common Stock Outstanding - diluted	237,883,881	[1]	237,767,071	[1]	236,294,812	[1]
Dividends Declared Per Share of Common Stock	$ 0.64		$ 0.49		$ 0.45
Nevada Power Company [Member]
OPERATING REVENUES:
OPERATING REVENUES	2,145,241		2,054,393		2,252,377
Operating Expenses
Fuel for power generation	407,687		498,487		588,419
Purchased power	472,715		477,226		505,239
Deferred energy	(67,976)		(16,300)		94,843
Energy efficiency program costs	81,845		37,292		0
Other operating expenses	267,720		260,127		260,535
Maintenance	74,364		64,320		71,759
Depreciation and amortization	269,721		252,191		226,252
Taxes other than income	36,870		37,254		37,918
Total Operating Expenses	1,542,946		1,610,597		1,784,965
OPERATING INCOME	602,295		443,796		467,412
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt)	(210,464)		(221,953)		(214,367)
Interest income (expense) on regulatory items	(6,768)		722		2,253
AFUDC - equity	6,522		8,298		25,229
Other income	17,418		5,480		10,119
Other expense	(13,152)		(33,020)		(12,946)
Total Other Income (Expense)	(206,444)		(240,473)		(189,712)
Income Before Income Tax Expense	395,851		203,323		277,700
Income Tax Expense (Benefit)	138,113		70,737		91,757
NET INCOME	257,738		132,586		185,943
Other comprehensive income (loss):
Change in compensation retirement benefits liability and amortization	(389)		(241)		(380)
COMPREHENSIVE INCOME	257,349		132,345		185,563
Sierra Pacific Power Company [Member]
OPERATING REVENUES:
Electric	725,874		716,417		836,879
Gas	108,046		172,482		190,943
OPERATING REVENUES	833,920		888,899		1,027,822
Operating Expenses
Fuel for power generation	157,694		182,098		233,065
Purchased power	131,284		156,648		143,642
Gas purchased for resale	74,352		125,155		137,702
Deferral of energy - electric-net	(26,369)		(65,445)		8,475
Deferral of energy - gas-net	(12,383)		(1,588)		9,789
Energy efficiency program costs	14,832		6,245		0
Other operating expenses	139,692		146,699		149,946
Maintenance	35,361		38,987		32,808
Depreciation and amortization	107,919		105,746		106,807
Taxes other than income	23,388		22,921		24,593
Total Operating Expenses	645,770		717,466		846,827
OPERATING INCOME	188,150		171,433		180,995
OTHER INCOME (EXPENSE):
Interest expense (net of AFUDC-debt)	(62,717)		(67,435)		(68,514)
Interest income (expense) on regulatory items	(954)		(4,838)		(5,948)
AFUDC - equity	2,624		2,575		2,883
Other income	5,365		3,972		13,348
Other expense	(7,893)		(14,624)		(9,985)
Total Other Income (Expense)	(63,575)		(80,350)		(68,216)
Income Before Income Tax Expense	124,575		91,083		112,779
Income Tax Expense (Benefit)	40,221		31,197		40,404
NET INCOME	84,354		59,886		72,375
Other comprehensive income (loss):
Change in compensation retirement benefits liability and amortization	(164)		1,236		(215)
COMPREHENSIVE INCOME	$ 84,190		$ 61,122		$ 72,160

[1] The denominator does not include stock equivalents for options issued under the non-qualified stock option plan due to conversion prices being higher than market prices for all periods. Under this plan, an additional 297,803, 390,095 and 563,624 shares for 2012, 2011 and 2010, respectively, would be included in each of these periods if the conditions for conversion were met.