CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury stock [Member]	Nevada Power Company [Member]	Nevada Power Company [Member] Common Stock [Member]	Nevada Power Company [Member] Additional Paid-in Capital [Member]	Nevada Power Company [Member] Retained Earnings [Member]	Nevada Power Company [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Sierra Pacific Power Company [Member]	Sierra Pacific Power Company [Member] Common Stock [Member]	Sierra Pacific Power Company [Member] Additional Paid-in Capital [Member]	Sierra Pacific Power Company [Member] Retained Earnings [Member]	Sierra Pacific Power Company [Member] Accumulated Other Comprehensive Income (Loss) [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2010	$ 3,350,818	$ 235,323	$ 2,705,954	$ 416,432	$ (6,891)		$ 2,761,632	$ 1	$ 2,254,219	$ 511,288	$ (3,876)	$ 973,420	$ 4	$ 1,111,262	$ (135,226)	$ (2,620)
Common stock, shares issued (in shares) at Dec. 31, 2010		235,322,553						1,000					1,000
Net Income	188,680			188,680			161,651			161,651		45,424			45,424
Dividend Reinvestment and Employee Benefits	8,369	677	7,692
Dividend Reinvestment and Employee Benefits (in shares)		677,196
Tax benefit from stock options exercised	312		312									312		312
Capital contribution from parent							54,000		54,000
Change in market value of risk management assets and liabilities	0
Change in compensation retirement benefits liability and amortization	2,417				2,417		1,028				1,028	2,230				2,230
Dividends Declared	(84,907)			(84,907)			(65,000)			(65,000)		(60,000)			(60,000)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2011	3,465,689	236,000	2,713,958	520,205	(4,474)		2,913,311	1	2,308,219	607,939	(2,848)	961,386	4	1,111,574	(149,802)	(390)
Common stock, shares issued (in shares) at Sep. 30, 2011		235,999,749						1,000					1,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2011
Net Income	173,462						154,608					25,336
Change in market value of risk management assets and liabilities	0
Change in compensation retirement benefits liability and amortization	544						75					279
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2011	3,465,689						2,913,311	1				961,386	4
Common stock, shares issued (in shares) at Sep. 30, 2011								1,000					1,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2011	3,406,079	236,000	2,713,736	464,277	(7,934)	0	2,848,977	1	2,308,219	544,874	(4,117)	974,542	4	1,111,262	(135,340)	(1,384)
Treasury stock (in shares) at Dec. 31, 2011	0					0
Common stock, shares issued (in shares) at Dec. 31, 2011	235,999,750	235,999,750					1,000	1,000				1,000	1,000
Net Income	304,782			304,782			256,151			256,151		65,750			65,750
Change in market value of risk management assets and liabilities	(668)				(668)
Change in compensation retirement benefits liability and amortization	464				464		192				192	127				127
Common stock repurchased						(252,000)
treasury stock value	4,509					(4,509)
Dividends Declared	(110,920)			(110,920)			(119,000)			(119,000)		(20,000)			(20,000)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2012	3,595,228	236,000	2,713,736	658,139	(8,138)	(4,509)	2,986,320	1	2,308,219	682,025	(3,925)	1,020,419	4	1,111,262	(89,590)	(1,257)
Treasury stock (in shares) at Sep. 30, 2012	(252,000)
Common stock, shares issued (in shares) at Sep. 30, 2012	235,999,750	235,999,750					1,000	1,000				1,000	1,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jun. 30, 2012
Net Income	223,170						195,170					34,427
Change in market value of risk management assets and liabilities	(193)
Change in compensation retirement benefits liability and amortization	155						65					42
treasury stock value	4,509
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2012	$ 3,595,228	$ 236,000	$ 2,713,736				$ 2,986,320	$ 1	$ 2,308,219			$ 1,020,419	$ 4	$ 1,111,262
Treasury stock (in shares) at Sep. 30, 2012	(252,000)
Common stock, shares issued (in shares) at Sep. 30, 2012	235,999,750	235,999,750					1,000	1,000				1,000	1,000