CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands, except Share data	Total	Nevada Power Company [Member]	Sierra Pacific Power Company [Member]	Common Stock [Member]	Common Stock [Member] Nevada Power Company [Member]	Common Stock [Member] Sierra Pacific Power Company [Member]	Other Paid-in Capital [Member]	Other Paid-in Capital [Member] Nevada Power Company [Member]	Other Paid-in Capital [Member] Sierra Pacific Power Company [Member]	Retained Earnings [Member]	Retained Earnings [Member] Nevada Power Company [Member]	Retained Earnings [Member] Sierra Pacific Power Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Nevada Power Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Sierra Pacific Power Company [Member]
Balance at Dec. 31, 2009	$ 3,223,922	$ 2,650,039	$ 1,009,258	$ 234,834	$ 1	$ 4	$ 2,700,329	$ 2,254,189	$ 1,111,260	$ 295,247	$ 399,345	$ (99,601)	$ (6,488)	$ (3,496)	$ (2,405)
Balance (in shares) at Dec. 31, 2009	234,834,169				1,000	1,000
Net Income (Loss)	35,225	17,458	28,435							35,225	17,458	28,435
Dividend Reinvestment and Employee Benefits	3,246			272			2,974
Dividend Reinvestment and Employee Benefits (in shares)				272,249
Change in compensation retirement benefits liability and amortization, net of taxes	63	33	17										63	33	17
Dividends, Common Stock, Cash	(51,693)	(53,000)	(25,000)							(51,693)	(53,000)	(25,000)
Balance at Jun. 30, 2010	3,210,763	2,614,530	1,012,710	235,106	1	4	2,703,303	2,254,189	1,111,260	278,779	363,803	(96,166)	(6,425)	(3,463)	(2,388)
Balance (in shares) at Jun. 30, 2010	235,106,418				1,000	1,000
Balance at Mar. 31, 2010
Net Income (Loss)	36,946	29,784	11,315
Balance at Jun. 30, 2010	3,210,763	2,614,530	1,012,710		1	4		2,254,189	1,111,260
Balance (in shares) at Jun. 30, 2010	235,106,418				1,000	1,000
Balance at Dec. 31, 2010	3,350,818	2,761,632	973,420	235,323	1	4	2,705,954	2,254,219	1,111,262	416,432	511,288	(135,226)	(6,891)	(3,876)	(2,620)
Balance (in shares) at Dec. 31, 2010	235,322,553				1,000	1,000
Net Income (Loss)	15,218	7,043	20,088							15,218	7,043	20,088
Capital contribution from parent		54,000						54,000
Dividend Reinvestment and Employee Benefits	8,072			654			7,418
Dividend Reinvestment and Employee Benefits (in shares)				654,489
Tax benefit from stock options exercised	312		312				312		312
Change in compensation retirement benefits liability and amortization, net of taxes	1,873	953	1,951										1,873	953	1,951
Dividends, Common Stock, Cash	(56,587)	(25,000)	(50,000)							(56,587)	(25,000)	(50,000)
Balance at Jun. 30, 2011	3,319,706	2,798,628	945,771	235,977	1	4	2,713,684	2,308,219	1,111,574	375,063	493,331	(165,138)	(5,018)	(2,923)	(669)
Balance (in shares) at Jun. 30, 2011	235,977,042				1,000	1,000
Balance at Mar. 31, 2011
Net Income (Loss)	12,888	16,063	3,512
Balance at Jun. 30, 2011	$ 3,319,706	$ 2,798,628	$ 945,771		$ 1	$ 4
Balance (in shares) at Jun. 30, 2011	235,977,042				1,000	1,000