CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 207,903	$ 145,944
Accounts receivable less allowance for uncollectible accounts	511,107	355,091
Materials, supplies and fuel, at average cost	147,984	129,663
Current income taxes receivable	0	82
Deferred income taxes	165,015	104,958
Other current assets	47,172	36,782
Total Current Assets	1,079,181	772,520
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	12,074,285	11,923,717
Construction work-in-progress	658,494	487,427
Total	12,732,779	12,411,144
Less accumulated provision for depreciation	3,351,132	3,184,071
Public Utilities, Property, Plant and Equipment, Net	9,381,647	9,227,073
Investments and other property, net	58,666	57,021
Other Assets, Noncurrent [Abstract]
Deferred energy	90,244	102,525
Regulatory assets	1,121,185	1,186,127
Regulatory asset for pension plans	207,137	215,656
Other Assets, Noncurrent	77,999	74,206
Total Deferred Charges and Other Assets	1,496,565	1,578,514
Assets	12,016,059	11,635,128
Current Liabilities:
Current maturities of long-term debt	258,024	139,985
Accounts Payable	322,940	312,990
Accrued expenses	101,199	128,144
Deferred energy	214,181	245,164
Other current liabilities	68,172	65,572
Total Current Liabilities	964,516	891,855
Long-term debt	4,766,563	5,008,931
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,546,998	1,306,510
Deferred investment tax credit	14,109	16,140
Accrued retirement benefits	79,405	92,351
Regulatory liabilities	541,823	486,259
Other deferred credits and liabilities	507,417	427,003
Total Deferred Credits and Other Liabilities	2,689,752	2,328,263
Shareholders' Equity
Common stock	236,000	236,000
Treasury stock, at cost	4,509	0
Other paid-in capital	2,713,736	2,713,736
Retained earnings	658,139	464,277
Accumulated other comprehensive loss	(8,138)	(7,934)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,595,228	3,406,079
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	12,016,059	11,635,128
Nevada Power Company [Member]
Current Assets:
Cash and cash equivalents	124,505	65,887
Accounts receivable less allowance for uncollectible accounts	397,954	233,096
Materials, supplies and fuel, at average cost	77,919	72,529
Deferred income taxes	132,663	88,782
Other current assets	32,658	28,943
Total Current Assets	765,699	489,237
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	8,396,240	8,345,771
Construction work-in-progress	519,218	352,541
Total	8,915,458	8,698,312
Less accumulated provision for depreciation	2,041,170	1,906,617
Public Utilities, Property, Plant and Equipment, Net	6,874,288	6,791,695
Investments and other property, net	51,875	50,768
Other Assets, Noncurrent [Abstract]
Deferred energy	90,244	102,525
Regulatory assets	820,372	852,989
Regulatory asset for pension plans	104,053	108,528
Other Assets, Noncurrent	59,060	46,855
Total Deferred Charges and Other Assets	1,073,729	1,110,897
Assets	8,765,591	8,442,597
Current Liabilities:
Current maturities of long-term debt	7,930	139,985
Accounts Payable	204,148	182,183
Accounts Payable, Related Parties, Current	42,915	28,429
Accrued expenses	60,942	89,311
Deferred energy	140,183	159,799
Other current liabilities	54,133	50,725
Total Current Liabilities	510,251	650,432
Long-term debt	3,328,281	3,319,605
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,187,617	997,921
Deferred investment tax credit	4,976	6,098
Accrued retirement benefits	13,163	9,454
Regulatory liabilities	317,993	274,951
Other deferred credits and liabilities	416,990	335,159
Total Deferred Credits and Other Liabilities	1,940,739	1,623,583
Shareholders' Equity
Common stock	1	1
Other paid-in capital	2,308,219	2,308,219
Retained earnings	682,025	544,874
Accumulated other comprehensive loss	(3,925)	(4,117)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,986,320	2,848,977
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	8,765,591	8,442,597
Sierra Pacific Power Company [Member]
Current Assets:
Cash and cash equivalents	51,736	55,195
Accounts receivable less allowance for uncollectible accounts	112,925	121,863
Materials, supplies and fuel, at average cost	70,065	57,134
Intercompany income taxes receivable	10,351	10,351
Deferred income taxes	42,464	32,311
Other current assets	14,019	7,504
Total Current Assets	301,560	284,358
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	3,678,045	3,577,946
Construction work-in-progress	139,276	134,886
Total	3,817,321	3,712,832
Less accumulated provision for depreciation	1,309,962	1,277,454
Public Utilities, Property, Plant and Equipment, Net	2,507,359	2,435,378
Investments and other property, net	6,438	5,901
Other Assets, Noncurrent [Abstract]
Regulatory assets	300,813	333,138
Regulatory asset for pension plans	100,270	104,159
Other Assets, Noncurrent	13,440	21,074
Total Deferred Charges and Other Assets	414,523	458,371
Assets	3,229,880	3,184,008
Current Liabilities:
Current maturities of long-term debt	250,094	0
Accounts Payable	83,714	99,897
Accounts Payable, Related Parties, Current	27,807	27,788
Accrued expenses	29,137	32,840
Deferred energy	73,998	85,365
Other current liabilities	14,040	14,846
Total Current Liabilities	478,790	260,736
Long-term debt	928,282	1,179,326
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	449,708	398,787
Deferred investment tax credit	9,133	10,042
Accrued retirement benefits	55,819	74,297
Regulatory liabilities	223,830	211,308
Other deferred credits and liabilities	63,899	74,970
Total Deferred Credits and Other Liabilities	802,389	769,404
Shareholders' Equity
Common stock	4	4
Other paid-in capital	1,111,262	1,111,262
Retained earnings	(89,590)	(135,340)
Accumulated other comprehensive loss	(1,257)	(1,384)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,020,419	974,542
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,229,880	$ 3,184,008