CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 84,708	$ 81,612
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	194,886	187,178
Deferred Income Taxes and Tax Credits	46,599	34,425
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(5,139)	(4,251)
Deferred energy	(162,179)	6,888
Amortization of other regulatory assets	85,882	75,711
Deferred rate increase	4,602	2,474
Other Noncash Income (Expense)	6,769	2,279
Changes in certain assets and liabilities:
Accounts receivable	(51,238)	(79,520)
Materials, supplies and fuel	7,771	(16,594)
Other current assets	(6,548)	1,518
Accounts payable	21,621	4,493
Increase (Decrease) in Pension and Postretirement Obligations	5,533	4,907
Other current liabilities	(4,535)	(4,875)
Other deferred assets	(2,400)	(2,700)
Other regulatory assets	(4,374)	10,058
Other deferred liabilities	6,185	(10,940)
Net Cash from Operating Activities	228,143	292,663
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(191,673)	(261,559)
Customer advances for construction	149	(847)
Contributions in aid of construction	27,975	45,106
Investments and other property - net	(5,005)	(128)
Net Cash used by Investing Activities	(168,554)	(217,428)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	(312)	130,590
Retirement of long-term debt	(2,459)	(158,201)
Sale of Common Stock	1,798	0
Common stock repurchased	(6,329)	0
Dividends paid	(89,490)	(70,800)
Net Cash from/(used by) Financing Activities	(96,792)	(98,411)
Net Increase in Cash and Cash Equivalents	(37,203)	(23,176)
Beginning Balance in Cash and Cash Equivalents	298,271	145,944
Ending Balance in Cash and Cash Equivalents	261,068	122,768
Cash paid during period for:
Interest	143,592	148,603
Income taxes	2	1
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	107,466	121,785
Issuance of treasury stock	12,793
Nevada Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	64,110	60,981
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	139,066	134,121
Deferred Income Taxes and Tax Credits	34,800	27,209
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(4,192)	(2,990)
Deferred energy	(106,527)	13,127
Amortization of other regulatory assets	47,490	36,659
Deferred rate increase	4,602	2,474
Other Noncash Income (Expense)	769	(213)
Changes in certain assets and liabilities:
Accounts receivable	(75,369)	(101,041)
Materials, supplies and fuel	368	(4,167)
Other current assets	(6,340)	3,159
Accounts payable	30,467	41,388
Increase (Decrease) in Pension and Postretirement Obligations	2,037	2,605
Other current liabilities	(1,238)	(3,342)
Other deferred assets	(990)	(1,973)
Other regulatory assets	(1,004)	24,720
Other deferred liabilities	541	(6,386)
Net Cash from Operating Activities	128,590	226,331
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(117,291)	(164,634)
Customer advances for construction	198	637
Contributions in aid of construction	10,118	25,383
Investments and other property - net	1,196	(144)
Net Cash used by Investing Activities	(105,779)	(138,758)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	(147)	132,083
Retirement of long-term debt	(2,180)	(157,491)
Dividends paid	(80,000)	(79,000)
Net Cash from/(used by) Financing Activities	(82,327)	(104,408)
Net Increase in Cash and Cash Equivalents	(59,516)	(16,835)
Beginning Balance in Cash and Cash Equivalents	201,202	65,887
Ending Balance in Cash and Cash Equivalents	141,686	49,052
Cash paid during period for:
Interest	101,242	105,973
Income taxes	1	1
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	86,745	98,358
Sierra Pacific Power Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	32,680	31,323
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, Depletion and Amortization, Nonproduction	55,820	53,057
Deferred Income Taxes and Tax Credits	16,759	11,894
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity	(947)	(1,261)
Deferred energy	(55,652)	(6,239)
Amortization of other regulatory assets	38,270	38,957
Other Noncash Income (Expense)	3,171	1,772
Changes in certain assets and liabilities:
Accounts receivable	24,140	21,543
Materials, supplies and fuel	7,403	(12,427)
Other current assets	127	(1,285)
Accounts payable	(7,303)	(27,583)
Increase (Decrease) in Pension and Postretirement Obligations	1,056	936
Other current liabilities	(1,030)	(1,251)
Other deferred assets	(1,410)	(727)
Other regulatory assets	(3,370)	(14,662)
Other deferred liabilities	(1,548)	(3,173)
Net Cash from Operating Activities	108,166	90,874
CASH FLOWS USED BY INVESTING ACTIVITIES:
Additions to utility plant (excluding AFUDC-equity)	(74,382)	(96,925)
Customer advances for construction	(49)	(1,484)
Contributions in aid of construction	17,857	19,723
Investments and other property - net	16	16
Net Cash used by Investing Activities	(56,558)	(78,670)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt	(165)	(1,446)
Retirement of long-term debt	(279)	(710)
Dividends paid	(20,000)	(20,000)
Net Cash from/(used by) Financing Activities	(20,444)	(22,156)
Net Increase in Cash and Cash Equivalents	31,164	(9,952)
Beginning Balance in Cash and Cash Equivalents	60,786	55,195
Ending Balance in Cash and Cash Equivalents	91,950	45,243
Cash paid during period for:
Interest	29,757	30,000
Noncash Investing and Financing Items [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	$ 20,721	$ 23,427