CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Treasury stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [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, 2009	$ 3,223,922	$ 234,834		$ 2,700,329	$ 295,247	$ (6,488)	$ 2,650,039	$ 1	$ 2,254,189	$ 399,345	$ (3,496)	$ 1,009,258	$ 4	$ 1,111,260	$ (99,601)	$ (2,405)
Balance (in shares) at Dec. 31, 2009		234,834,169						1,000					1,000
Net Income	226,984				226,984		185,943			185,943		72,375			72,375
Employee Benefits	6,109	489		5,620
Dividend Reinvestment and Employee Benefits (in shares)		488,384
Tax benefit from stock options exercised	32			32			30		30			2		2
Change in market value of risk management assets and liabilities	0
Change in compensation retirement benefits liability and amortization	403					(403)	(380)				(380)	(215)				(215)
Common stock issuance costs	(27)			(27)
Dividends Declared	(105,799)				(105,799)		(74,000)			(74,000)		(108,000)			(108,000)
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)
Balance (in shares) at Dec. 31, 2010		235,322,553						1,000					1,000
Net Income	2,330						(9,020)					16,576
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2011
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		(135,226)	(2,620)
Balance (in shares) at Dec. 31, 2010		235,322,553						1,000					1,000
Net Income	163,432				163,432		132,586			132,586		59,886			59,886
Employee Benefits	8,459	677		7,782
Dividend Reinvestment and Employee Benefits (in shares)		677,197
Capital contribution from parent							54,000		54,000
Change in market value of risk management assets and liabilities	(686)					(686)
Change in compensation retirement benefits liability and amortization	357					(357)	(241)				(241)	1,236				1,236
Dividends Declared	(115,587)				(115,587)		(99,000)			(99,000)		(60,000)			(60,000)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2011	3,406,079	236,000		2,713,736	464,277	(7,934)	2,848,977	1	2,308,219	544,874	(4,117)	974,542	4		(135,340)	(1,384)
Balance (in shares) at Dec. 31, 2011	235,999,750	235,999,750					1,000	1,000					1,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2011
Net Income	(25,248)						(29,065)					14,462
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2011	3,406,079						2,848,977	1				974,542	4
Balance (in shares) at Dec. 31, 2011	235,999,750						1,000	1,000					1,000
Net Income	12,173						(1,316)					18,644
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Mar. 31, 2012
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2011	3,406,079			2,713,736	464,277	(7,934)	2,848,977	1	2,308,219	544,874	(4,117)	974,542	4	1,111,262	(135,340)	(1,384)
Balance (in shares) at Dec. 31, 2011	235,999,750						1,000	1,000					1,000
Net Income	321,946				321,946		257,738			257,738		84,354			84,354
Employee Benefits	2,329		3,127	(798)
Dividend Reinvestment and Employee Benefits (in shares)			171,706
Tax benefit from stock options exercised	5			5			(8)		(8)			4		4
Change in market value of risk management assets and liabilities	(539)					(539)
Change in compensation retirement benefits liability and amortization	1,598					(1,598)	(389)				(389)	(164)				(164)
Dividends Declared	(150,920)				(150,920)		(184,000)			(184,000)		(20,000)			(20,000)
Common stock repurchased	(19,931)		(19,931)
Common stock repurchaed (shares)	1,100,000		(1,092,300)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2012	3,557,371	236,000	(16,804)	2,712,943	635,303	(10,071)	2,922,318	1	2,308,211	618,612	(4,506)	1,038,736	4	1,111,266	(70,986)	(1,548)
Balance (in shares) at Dec. 31, 2012	235,079,156	235,999,750	(920,594)				1,000	1,000					1,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Sep. 30, 2012
Net Income	17,164						1,587					18,604
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Dec. 31, 2012	$ 3,557,371	$ 236,000					$ 2,922,318	$ 1				$ 1,038,736	$ 4
Balance (in shares) at Dec. 31, 2012	235,079,156	235,999,750					1,000	1,000					1,000