CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
CASH FLOWS FROM (USED BY) OPERATING ACTIVITIES
Net Income	$ 304,782	$ 188,680
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	281,690	266,445
Deferred Income Taxes and Tax Credits	187,229	99,920
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(6,666)	(12,854)
Deferred energy	(18,702)	(20,802)
Amortization of other regulatory assets	114,626	124,213
Deferred rate increase	2,252	65,306
Other Noncash Income (Expense)	(50,012)	27,546
Changes in certain assets and liabilities:
Accounts receivable	(151,420)	(132,078)
Materials, supplies and fuel	(18,034)	(26,290)
Other current assets	(10,390)	(5,242)
Accounts payable	22,646	32,397
Accrued Retirement Benefits	(12,946)	167
Other current liabilities	(23,643)	(37,869)
Other deferred assets	(3,572)	(14,982)
Other regulatory assets	34,420	(72,480)
Other deferred liabilities	(8,066)	(15,043)
Net Cash from Operating Activities	644,194	467,034
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(387,790)	(469,870)
Proceeds from Sale of Other Property, Plant, and Equipment	0	166,603
Customer advances for construction	(1,508)	(7,159)
Contributions in aid of construction	63,864	79,343
Investments and other property - net	217	410
Net Cash used by Investing Activities	(325,217)	(230,673)
CASH FLOWS FROM (USED BY) FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	130,764	386,784
Retirement of long-term debt	(272,353)	(480,689)
Settlement of interest rate lock	0	(14,944)
Sale of Common Stock	0	8,681
Common stock repurchased	(4,509)	0
Dividends paid	(110,920)	(84,907)
Net Cash from (used by) Financing Activities	(257,018)	(185,075)
Net Increase (Decrease) in Cash and Cash Equivalents	61,959	51,286
Beginning Balance in Cash and Cash Equivalents	145,944	86,189
Ending Balance in Cash and Cash Equivalents	207,903	137,475
Cash paid during period for:
Interest	237,262	251,011
Income taxes	151	1
Significant non-cash transactions:
Accrued Construction Expenses	132,112	158,849
Nevada Power Company [Member]
CASH FLOWS FROM (USED BY) OPERATING ACTIVITIES
Net Income	256,151	161,651
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	201,096	186,798
Deferred Income Taxes and Tax Credits	150,289	85,488
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(4,823)	(10,979)
Deferred energy	(7,335)	14,651
Amortization of other regulatory assets	56,012	62,994
Deferred rate increase	2,252	65,306
Other Noncash Income (Expense)	(35,553)	19,889
Changes in certain assets and liabilities:
Accounts receivable	(164,858)	(145,862)
Materials, supplies and fuel	(5,119)	(9,100)
Other current assets	(3,715)	(3,307)
Accounts payable	53,985	26,434
Accrued Retirement Benefits	3,708	3,971
Other current liabilities	(25,246)	(32,523)
Other deferred assets	(2,412)	(13,788)
Other regulatory assets	50,008	(44,383)
Other deferred liabilities	(10,412)	(16,676)
Net Cash from Operating Activities	514,028	350,564
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(232,608)	(367,097)
Proceeds from Sale of Other Property, Plant, and Equipment	0	31,997
Customer advances for construction	713	(2,165)
Contributions in aid of construction	34,274	64,617
Investments and other property - net	193	395
Net Cash used by Investing Activities	(197,428)	(272,253)
CASH FLOWS FROM (USED BY) FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	132,259	386,884
Retirement of long-term debt	(271,241)	(464,575)
Additional investment by parent company	0	54,000
Settlement of interest rate lock	0	(14,944)
Dividends paid	(119,000)	(65,000)
Net Cash from (used by) Financing Activities	(257,982)	(103,635)
Net Increase (Decrease) in Cash and Cash Equivalents	58,618	(25,324)
Beginning Balance in Cash and Cash Equivalents	65,887	60,077
Ending Balance in Cash and Cash Equivalents	124,505	34,753
Cash paid during period for:
Interest	177,459	182,992
Income taxes	1	1
Significant non-cash transactions:
Accrued Construction Expenses	111,052	141,384
Sierra Pacific Power Company [Member]
CASH FLOWS FROM (USED BY) OPERATING ACTIVITIES
Net Income	65,750	45,424
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	80,594	79,647
Deferred Income Taxes and Tax Credits	42,809	23,296
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(1,843)	(1,875)
Deferred energy	(11,367)	(35,453)
Amortization of other regulatory assets	58,484	59,855
Other Noncash Income (Expense)	(15,532)	8,546
Changes in certain assets and liabilities:
Accounts receivable	13,452	13,917
Materials, supplies and fuel	(12,915)	(17,190)
Other current assets	(6,512)	(964)
Accounts payable	(21,002)	12,833
Accrued Retirement Benefits	(18,477)	(4,504)
Other current liabilities	(3,522)	(6,447)
Other deferred assets	(1,160)	(1,194)
Other regulatory assets	(15,588)	(28,097)
Other deferred liabilities	(6,282)	(2,501)
Net Cash from Operating Activities	146,889	145,293
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(155,182)	(102,773)
Proceeds from Sale of Other Property, Plant, and Equipment	0	134,606
Customer advances for construction	(2,221)	(4,994)
Contributions in aid of construction	29,590	14,726
Investments and other property - net	24	15
Net Cash used by Investing Activities	(127,789)	41,580
CASH FLOWS FROM (USED BY) FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	(1,447)	0
Retirement of long-term debt	(1,112)	(16,114)
Dividends paid	(20,000)	(114,000)
Net Cash from (used by) Financing Activities	(22,559)	(130,114)
Net Increase (Decrease) in Cash and Cash Equivalents	(3,459)	56,759
Beginning Balance in Cash and Cash Equivalents	55,195	9,552
Ending Balance in Cash and Cash Equivalents	51,736	66,311
Cash paid during period for:
Interest	45,772	45,632
Significant non-cash transactions:
Accrued Construction Expenses	$ 21,060	$ 17,465