CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 321,946	$ 163,432	$ 226,984
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	377,640	357,937	333,059
Deferred Income Taxes and Tax Credits	186,712	88,445	129,231
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(9,146)	(10,873)	(28,112)
Deferred energy	(92,847)	(55,429)	147,497
Gain (Loss) on Sale of Investments	(4,384)	0	(7,575)
Amortization of other regulatory assets	163,479	166,095	110,654
Deferred rate increase	3,830	79,866	(8,343)
Other Noncash Income (Expense)	(29,382)	20,346	(8,399)
Changes in certain assets and liabilities:
Accounts receivable	(19,310)	215	52,238
Materials, supplies and fuel	(8,297)	(14,747)	9,167
Other current assets	(3,969)	5,548	1,969
Accounts payable	12,405	17,466	28,070
Increase (Decrease) in Pension and Postretirement Obligations	(10,120)	(26,845)	(18,476)
Other current liabilities	4,627	(14,449)	2,945
Other deferred assets	(3,926)	(6,430)	(6,111)
Other regulatory assets	(13,727)	(113,568)	(77,893)
Other deferred liabilities	(982)	1,369	(453)
Net Cash from Operating Activities	874,549	658,378	886,452
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(498,893)	(620,516)	(629,496)
Proceeds from Sale of Other Property, Plant, and Equipment	0	166,603	18,225
Customer advances for construction	(1,548)	(7,762)	(11,142)
Contributions in aid of construction	86,171	106,050	63,330
Investments and other property - net	246	498	(8,974)
Net Cash used by Investing Activities	(414,024)	(355,127)	(568,057)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	130,485	579,820	985,419
Retirement of long-term debt	(270,959)	(701,244)	(1,180,646)
Settlement of interest rate lock	0	(14,944)	0
Sale of Common Stock	2,307	8,459	6,114
Common stock repurchased	(19,111)	0	0
Dividends paid	(150,920)	(115,587)	(105,799)
Net Cash from/(used by) Financing Activities	(308,198)	(243,496)	(294,912)
Net Increase in Cash and Cash Equivalents	152,327	59,755	23,483
Beginning Balance in Cash and Cash Equivalents	145,944	86,189	62,706
Ending Balance in Cash and Cash Equivalents	298,271	145,944	86,189
Cash paid during period for:
Interest	292,561	314,401	336,668
Income taxes	151	576	754
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	176,940	195,511	86,127
Capital Lease Obligations Incurred	0	0	15,336
Transfer of assets to accounts receivable	0	0	16,830
Nevada Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	257,738	132,586	185,943
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	269,721	252,191	226,252
Deferred Income Taxes and Tax Credits	150,634	71,971	92,859
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(6,522)	(8,298)	(25,229)
Deferred energy	(58,245)	3,549	116,230
Gain (Loss) on Sale of Investments	(4,384)	0	0
Amortization of other regulatory assets	87,815	83,070	74,625
Deferred rate increase	3,830	79,866	(8,343)
Other Noncash Income (Expense)	(28,167)	9,372	(6,588)
Changes in certain assets and liabilities:
Accounts receivable	(14,910)	(8,391)	39,679
Materials, supplies and fuel	(4,786)	(5,674)	3,115
Other current assets	181	736	(1,824)
Accounts payable	35,460	(11)	13,905
Increase (Decrease) in Pension and Postretirement Obligations	4,894	(9,725)	(17,792)
Other current liabilities	2,405	(7,888)	4,959
Other deferred assets	(2,592)	(5,125)	(2,598)
Other regulatory assets	20,575	(54,885)	(50,937)
Other deferred liabilities	(10,996)	(6,235)	(2,873)
Net Cash from Operating Activities	702,651	527,109	641,383
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(287,598)	(475,118)	(499,374)
Proceeds from Sale of Other Property, Plant, and Equipment	0	31,997	3,254
Customer advances for construction	1,016	(1,852)	(8,646)
Contributions in aid of construction	41,368	89,427	55,140
Investments and other property - net	215	475	(5)
Net Cash used by Investing Activities	(244,999)	(355,071)	(449,631)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	132,259	386,884	637,463
Retirement of long-term debt	(270,596)	(493,168)	(737,747)
Additional investment by parent company	0	54,000	0
Settlement of interest rate lock	0	(14,944)	0
Dividends paid	(184,000)	(99,000)	(74,000)
Net Cash from/(used by) Financing Activities	(322,337)	(166,228)	(174,284)
Net Increase in Cash and Cash Equivalents	135,315	5,810	17,468
Beginning Balance in Cash and Cash Equivalents	65,887	60,077	42,609
Ending Balance in Cash and Cash Equivalents	201,202	65,887	60,077
Cash paid during period for:
Interest	207,530	218,693	226,138
Income taxes	1	1	2
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	149,507	175,661	74,557
Capital Lease Obligations Incurred	0	0	15,336
Sierra Pacific Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	84,354	59,886	72,375
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	107,919	105,746	106,807
Deferred Income Taxes and Tax Credits	47,912	31,487	39,220
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(2,624)	(2,575)	(2,883)
Deferred energy	(34,602)	(58,978)	31,267
Gain (Loss) on Sale of Investments	0	0	(7,575)
Amortization of other regulatory assets	75,498	81,636	35,799
Other Noncash Income (Expense)	(1,785)	8,995	(5,227)
Changes in certain assets and liabilities:
Accounts receivable	(4,481)	8,739	31,961
Materials, supplies and fuel	(3,511)	(9,073)	5,991
Other current assets	(4,126)	4,128	4,421
Accounts payable	(9,427)	26,564	2,050
Increase (Decrease) in Pension and Postretirement Obligations	(17,245)	(18,401)	(2,523)
Other current liabilities	(109)	(2,131)	721
Other deferred assets	(1,334)	(1,305)	(3,513)
Other regulatory assets	(34,302)	(58,683)	(26,956)
Other deferred liabilities	(5,431)	641	887
Net Cash from Operating Activities	196,706	176,676	282,822
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(211,295)	(145,398)	(143,216)
Proceeds from Sale of Other Property, Plant, and Equipment	0	134,606	14,971
Customer advances for construction	(2,564)	(5,910)	(2,496)
Contributions in aid of construction	44,803	16,623	8,190
Investments and other property - net	31	23	(97)
Net Cash used by Investing Activities	(169,025)	(56)	(122,648)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	(1,727)	(403)	37,726
Retirement of long-term debt	(363)	(16,574)	(148,707)
Dividends paid	(20,000)	(114,000)	(54,000)
Net Cash from/(used by) Financing Activities	(22,090)	(130,977)	(164,981)
Net Increase in Cash and Cash Equivalents	5,591	45,643	(4,807)
Beginning Balance in Cash and Cash Equivalents	55,195	9,552	14,359
Ending Balance in Cash and Cash Equivalents	60,786	55,195	9,552
Cash paid during period for:
Interest	59,772	59,605	67,351
Income taxes	150	575	752
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	27,433	19,850	11,570
Transfer of assets to accounts receivable	0	0	16,830
Dividends	$ 0	$ 0	$ 54,000