CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Unaudited) (USD $)	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	$ 3,223,923,000		$ 2,650,039,000	$ 1,009,258,000	$ 234,834,000	$ 1,000	$ 4,000	$ 2,700,329,000	$ 2,254,189,000	$ 1,111,260,000	$ 295,248,000	$ 399,345,000	$ (99,601,000)	$ (6,488,000)	$ (3,496,000)	$ (2,405,000)
Balance (in shares) at Dec. 31, 2009	234,834,169		1,000	1,000	234,834,169
Net Income (Loss)	212,771,000	[1]	176,386,000	52,897,000							212,771,000	176,386,000	52,897,000
Dividend Reinvestment and Employee Benefits	4,087,000				339,000			3,748,000
Dividend Reinvestment and Employee Benefits (in shares)					338,455
Change in compensation retirement benefits liability and amortization, net of taxes	94,000		50,000	26,000										94,000	50,000	26,000
Dividends, Common Stock, Cash	(77,561,000)		(62,000,000)	(48,000,000)							(77,561,000)	(62,000,000)	(48,000,000)
Balance at Sep. 30, 2010	3,363,314,000		2,764,475,000	1,014,181,000	235,173,000	1,000	4,000	2,704,077,000	2,254,189,000	1,111,260,000	430,458,000	513,731,000	(94,704,000)	(6,394,000)	(3,446,000)	(2,379,000)
Balance (in shares) at Sep. 30, 2010	235,172,624		1,000	1,000	235,172,624
Balance at Jun. 30, 2010
Net Income (Loss)	177,546,000	[1]	158,928,000	24,462,000
Balance at Sep. 30, 2010	3,363,314,000		2,764,475,000	1,014,181,000		1,000	4,000		2,254,189,000	1,111,260,000
Balance (in shares) at Sep. 30, 2010	235,172,624		1,000	1,000
Balance at Dec. 31, 2010	3,350,818,000		2,761,632,000	973,420,000	235,323,000	1,000	4,000	2,705,954,000	2,254,219,000	1,111,262,000	416,432,000	511,288,000	(135,226,000)	(6,891,000)	(3,876,000)	(2,620,000)
Balance (in shares) at Dec. 31, 2010	235,322,553		1,000	1,000
Net Income (Loss)	188,680,000		161,651,000	45,424,000							188,680,000	161,651,000	45,424,000
Capital contribution from parent			54,000,000						54,000,000
Dividend Reinvestment and Employee Benefits	8,369,000				677,000			7,692,000
Dividend Reinvestment and Employee Benefits (in shares)					677,196
Tax benefit from stock options exercised	312,000			312,000				312,000		312,000
Change in compensation retirement benefits liability and amortization, net of taxes	2,417,000		1,028,000	2,230,000										2,417,000	1,028,000	2,230,000
Dividends, Common Stock, Cash	(84,907,000)		(65,000,000)	(60,000,000)							(84,907,000)	(65,000,000)	(60,000,000)
Balance at Sep. 30, 2011	3,465,689,000		2,913,311,000	961,386,000	236,000,000	1,000	4,000	2,713,958,000	2,308,219,000	1,111,574,000	520,205,000	607,939,000	(149,802,000)	(4,474,000)	(2,848,000)	(390,000)
Balance (in shares) at Sep. 30, 2011	235,999,749		1,000	1,000
Balance at Jun. 30, 2011
Net Income (Loss)	173,462,000		154,608,000	25,336,000
Balance at Sep. 30, 2011	$ 3,465,689,000		$ 2,913,311,000	$ 961,386,000		$ 1,000	$ 4,000
Balance (in shares) at Sep. 30, 2011	235,999,749		1,000	1,000

[1] As discussed in Note 1, Summary of Significant Accounting Policies, net income and earnings per share basic and diluted were reduced from that previously reported by $5.2 million (net of taxes) and $0.02 per share (net of taxes), respectively.