CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current Assets:
Cash and cash equivalents	$ 298,271	$ 145,944
Accounts receivable less allowance for uncollectible accounts	373,099	355,091
Materials, supplies and fuel, at average cost	138,337	129,663
Current income taxes receivable	0	82
Deferred income taxes (Note 10)	60,592	104,958
Other current assets	40,750	36,782
Total Current Assets	911,049	772,520
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	12,031,053	11,923,717
Construction work-in-progress	708,109	487,427
Total (Note 1)	12,739,162	12,411,144
Less accumulated provision for depreciation	3,313,188	3,184,071
Public Utilities, Property, Plant and Equipment, Net	9,425,974	9,227,073
Investments and other property, net (Note 4)	56,660	57,021
Other Assets, Noncurrent [Abstract]
Deferred energy (Note 3)	87,072	102,525
Regulatory assets (Note 3)	1,132,768	1,218,128
Regulatory asset for pension plans (Note 3)	281,195	215,656
Other Assets, Noncurrent	89,418	74,206
Total Deferred Charges and Other Assets	1,590,453	1,610,515
Assets	11,984,136	11,667,129
Current Liabilities:
Current maturities of long-term debt (Note 6)	356,283	139,985
Accounts Payable	332,245	312,990
Accrued expenses	127,693	128,144
Deferred energy (Note 3)	136,865	245,164
Other current liabilities	66,221	65,572
Total Current Liabilities	1,019,307	891,855
Long-term debt (Note 6)	4,669,798	5,008,931
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes (Note 10)	1,470,973	1,338,511
Deferred investment tax credit	13,538	16,140
Accrued retirement benefits	162,260	92,351
Regulatory liabilities (Note 3)	550,687	486,259
Other deferred credits and liabilities	540,202	427,003
Total Deferred Credits and Other Liabilities	2,737,660	2,360,264
Shareholders' Equity
Common stock	236,000	236,000
Treasury stock, at cost	16,804	0
Other paid-in capital	2,712,943	2,713,736
Retained earnings	635,303	464,277
Accumulated other comprehensive loss	(10,071)	(7,934)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,557,371	3,406,079
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	11,984,136	11,667,129
Nevada Power Company [Member]
Current Assets:
Cash and cash equivalents	201,202	65,887
Accounts receivable less allowance for uncollectible accounts	248,501	233,096
Materials, supplies and fuel, at average cost	77,675	72,529
Deferred income taxes (Note 10)	48,590	88,782
Other current assets	28,763	28,943
Total Current Assets	604,731	489,237
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	8,363,566	8,345,771
Construction work-in-progress	567,941	352,541
Total (Note 1)	8,931,507	8,698,312
Less accumulated provision for depreciation	2,035,322	1,906,617
Public Utilities, Property, Plant and Equipment, Net	6,896,185	6,791,695
Investments and other property, net (Note 4)	49,808	50,768
Other Assets, Noncurrent [Abstract]
Deferred energy (Note 3)	87,072	102,525
Regulatory assets (Note 3)	804,013	852,989
Regulatory asset for pension plans (Note 3)	136,682	108,528
Other Assets, Noncurrent	62,654	46,855
Total Deferred Charges and Other Assets	1,090,421	1,110,897
Assets	8,641,145	8,442,597
Current Liabilities:
Current maturities of long-term debt (Note 6)	106,048	139,985
Accounts Payable	201,193	182,183
Accounts Payable, Related Parties, Current	42,036	28,429
Accrued expenses	86,433	89,311
Deferred energy (Note 3)	86,102	159,799
Other current liabilities	52,567	50,725
Total Current Liabilities	574,379	650,432
Long-term debt (Note 6)	3,230,808	3,319,605
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes (Note 10)	1,101,804	997,921
Deferred investment tax credit	4,688	6,098
Accrued retirement benefits	49,381	9,454
Regulatory liabilities (Note 3)	323,400	274,951
Other deferred credits and liabilities	434,367	335,159
Total Deferred Credits and Other Liabilities	1,913,640	1,623,583
Shareholders' Equity
Common stock	1	1
Other paid-in capital	2,308,211	2,308,219
Retained earnings	618,612	544,874
Accumulated other comprehensive loss	(4,506)	(4,117)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,922,318	2,848,977
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	8,641,145	8,442,597
Sierra Pacific Power Company [Member]
Current Assets:
Cash and cash equivalents	60,786	55,195
Accounts receivable less allowance for uncollectible accounts	124,464	121,863
Materials, supplies and fuel, at average cost	60,662	57,134
Intercompany income taxes receivable	10,351	10,351
Deferred income taxes (Note 10)	21,589	32,311
Other current assets	11,633	7,504
Total Current Assets	289,485	284,358
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	3,667,487	3,577,946
Construction work-in-progress	140,168	134,886
Total (Note 1)	3,807,655	3,712,832
Less accumulated provision for depreciation	1,277,866	1,277,454
Public Utilities, Property, Plant and Equipment, Net	2,529,789	2,435,378
Investments and other property, net (Note 4)	6,499	5,901
Other Assets, Noncurrent [Abstract]
Regulatory assets (Note 3)	328,755	365,139
Regulatory asset for pension plans (Note 3)	140,268	104,159
Other Assets, Noncurrent	21,477	21,074
Total Deferred Charges and Other Assets	490,500	490,372
Assets	3,316,273	3,216,009
Current Liabilities:
Current maturities of long-term debt (Note 6)	250,235	0
Accounts Payable	106,415	99,897
Accounts Payable, Related Parties, Current	21,534	27,788
Accrued expenses	32,936	32,840
Deferred energy (Note 3)	50,763	85,365
Other current liabilities	13,655	14,846
Total Current Liabilities	475,538	260,736
Long-term debt (Note 6)	928,990	1,179,326
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes (Note 10)	465,508	430,788
Deferred investment tax credit	8,850	10,042
Accrued retirement benefits	98,676	74,297
Regulatory liabilities (Note 3)	227,287	211,308
Other deferred credits and liabilities	72,688	74,970
Total Deferred Credits and Other Liabilities	873,009	801,405
Shareholders' Equity
Common stock	4	4
Other paid-in capital	1,111,266	1,111,262
Retained earnings	(70,986)	(135,340)
Accumulated other comprehensive loss	(1,548)	(1,384)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,038,736	974,542
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,316,273	$ 3,216,009