CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 21,475	$ 12,173
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	96,002	90,862
Deferred Income Taxes and Tax Credits	11,956	(5,183)
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(2,889)	(1,932)
Deferred energy	(77,578)	(9,134)
Amortization of other regulatory assets	41,621	39,028
Deferred rate increase	2,103	2,691
Other Noncash Income (Expense)	(897)	1,575
Changes in certain assets and liabilities:
Accounts receivable	68,131	31,208
Materials, supplies and fuel	4,815	(874)
Other current assets	(13,648)	(13,021)
Accounts payable	(29,795)	(37,825)
Increase (Decrease) in Pension and Postretirement Obligations	2,055	2,221
Other current liabilities	(29,335)	(29,348)
Other deferred assets	(1,263)	(1,602)
Other regulatory assets	(2,379)	4,164
Other deferred liabilities	(1,480)	(17,687)
Net Cash from Operating Activities	88,894	67,316
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(97,948)	(115,817)
Customer advances for construction	(629)	(184)
Contributions in aid of construction	13,570	26,052
Investments and other property - net	111	48
Net Cash used by Investing Activities	(84,896)	(89,901)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	0	10,951
Retirement of long-term debt	(3,671)	(3,295)
Sale of Common Stock	754	0
Common stock repurchased	(3,651)	0
Dividends paid	(44,748)	(30,680)
Net Cash from/(used by) Financing Activities	(51,316)	(23,024)
Net Increase in Cash and Cash Equivalents	(47,318)	(45,609)
Beginning Balance in Cash and Cash Equivalents	298,271	145,944
Ending Balance in Cash and Cash Equivalents	250,953	100,335
Cash paid during period for:
Interest	88,337	88,606
Income taxes	2	0
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	61,262	85,850
Issuance of treasury stock	11,041
Nevada Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	5,445	(1,316)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	68,661	64,990
Deferred Income Taxes and Tax Credits	2,949	(6,349)
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(2,366)	(1,413)
Deferred energy	(44,235)	4,050
Amortization of other regulatory assets	22,119	18,301
Deferred rate increase	2,103	2,691
Other Noncash Income (Expense)	(4,261)	(796)
Changes in certain assets and liabilities:
Accounts receivable	50,792	22,441
Materials, supplies and fuel	(3,232)	(2,209)
Other current assets	(9,246)	(8,674)
Accounts payable	(24,421)	(14,248)
Increase (Decrease) in Pension and Postretirement Obligations	947	1,572
Other current liabilities	(25,097)	(27,419)
Other deferred assets	(491)	(1,288)
Other regulatory assets	(801)	9,880
Other deferred liabilities	(1,348)	(7,495)
Net Cash from Operating Activities	37,518	52,718
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(59,357)	(66,843)
Customer advances for construction	(749)	654
Contributions in aid of construction	6,890	15,951
Investments and other property - net	103	40
Net Cash used by Investing Activities	(53,113)	(50,198)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	0	12,432
Retirement of long-term debt	(3,391)	(3,129)
Dividends paid	(50,000)	(39,000)
Net Cash from/(used by) Financing Activities	(53,391)	(29,697)
Net Increase in Cash and Cash Equivalents	(68,986)	(27,177)
Beginning Balance in Cash and Cash Equivalents	201,202	65,887
Ending Balance in Cash and Cash Equivalents	132,216	38,710
Cash paid during period for:
Interest	71,187	71,276
Income taxes	1	0
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	48,812	72,179
Sierra Pacific Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	21,904	18,644
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	27,341	25,872
Deferred Income Taxes and Tax Credits	11,707	3,537
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(523)	(519)
Deferred energy	(33,343)	(13,184)
Amortization of other regulatory assets	19,441	20,668
Other Noncash Income (Expense)	2,099	2,249
Changes in certain assets and liabilities:
Accounts receivable	17,331	8,869
Materials, supplies and fuel	8,047	1,335
Other current assets	(4,635)	(4,564)
Accounts payable	(3,198)	(17,675)
Increase (Decrease) in Pension and Postretirement Obligations	280	367
Other current liabilities	(5,757)	(5,388)
Other deferred assets	(772)	(314)
Other regulatory assets	(1,578)	(5,716)
Other deferred liabilities	(1,787)	(4,214)
Net Cash from Operating Activities	56,557	29,967
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(38,591)	(48,974)
Customer advances for construction	120	(838)
Contributions in aid of construction	6,680	10,101
Investments and other property - net	8	8
Net Cash used by Investing Activities	(31,783)	(39,703)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	0	(1,441)
Retirement of long-term debt	(280)	(166)
Dividends paid	0	(20,000)
Net Cash from/(used by) Financing Activities	(280)	(21,607)
Net Increase in Cash and Cash Equivalents	24,494	(31,343)
Beginning Balance in Cash and Cash Equivalents	60,786	55,195
Ending Balance in Cash and Cash Equivalents	85,280	23,852
Cash paid during period for:
Interest	15,780	15,944
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	$ 12,450	$ 13,671