CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 250,953	$ 298,271
Accounts receivable less allowance for uncollectible accounts	317,191	373,099
Materials, supplies and fuel, at average cost	133,613	138,337
Deferred income taxes	88,648	60,592
Other current assets	54,397	40,750
Total Current Assets	844,802	911,049
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	12,077,001	12,031,053
Construction work-in-progress	730,262	708,109
Total	12,807,263	12,739,162
Less accumulated provision for depreciation	3,378,468	3,313,188
Public Utilities, Property, Plant and Equipment, Net	9,428,795	9,425,974
Investments and other property, net	58,389	56,660
Other Assets, Noncurrent [Abstract]
Deferred energy	84,120	87,072
Regulatory assets	1,102,348	1,132,768
Regulatory asset for pension plans	277,836	281,195
Other Assets, Noncurrent	82,343	89,418
Total Deferred Charges and Other Assets	1,546,647	1,590,453
Assets	11,878,633	11,984,136
Current Liabilities:
Current maturities of long-term debt	481,342	356,283
Accounts Payable	280,206	332,245
Accrued expenses	95,080	127,693
Deferred energy	56,336	136,865
Other current liabilities	69,306	66,221
Total Current Liabilities	982,270	1,019,307
Long-term debt	4,541,241	4,669,798
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,510,369	1,470,973
Deferred investment tax credit	12,984	13,538
Accrued retirement benefits	164,315	162,260
Regulatory liabilities	558,692	550,687
Other deferred credits and liabilities	564,911	540,202
Total Deferred Credits and Other Liabilities	2,811,271	2,737,660
Shareholders' Equity
Common stock	236,000	236,000
Treasury stock, at cost	(8,660)	(16,804)
Other paid-in capital	2,714,107	2,712,943
Retained earnings	612,030	635,303
Accumulated other comprehensive loss	(9,626)	(10,071)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,543,851	3,557,371
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	11,878,633	11,984,136
Nevada Power Company [Member]
Current Assets:
Cash and cash equivalents	132,216	201,202
Accounts receivable less allowance for uncollectible accounts	198,740	248,501
Materials, supplies and fuel, at average cost	80,998	77,675
Deferred income taxes	80,265	48,590
Other current assets	38,008	28,763
Total Current Assets	530,227	604,731
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	8,399,239	8,363,566
Construction work-in-progress	603,495	567,941
Total	9,002,734	8,931,507
Less accumulated provision for depreciation	2,091,598	2,035,322
Public Utilities, Property, Plant and Equipment, Net	6,911,136	6,896,185
Investments and other property, net	51,201	49,808
Other Assets, Noncurrent [Abstract]
Deferred energy	84,120	87,072
Regulatory assets	781,916	804,013
Regulatory asset for pension plans	135,191	136,682
Other Assets, Noncurrent	64,924	62,654
Total Deferred Charges and Other Assets	1,066,151	1,090,421
Assets	8,558,715	8,641,145
Current Liabilities:
Current maturities of long-term debt	231,075	106,048
Accounts Payable	168,582	201,193
Accounts Payable, Related Parties, Current	39,650	42,036
Accrued expenses	58,774	86,433
Deferred energy	38,915	86,102
Other current liabilities	54,935	52,567
Total Current Liabilities	591,931	574,379
Long-term debt	3,102,390	3,230,808
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,136,115	1,101,804
Deferred investment tax credit	4,407	4,688
Accrued retirement benefits	50,328	49,381
Regulatory liabilities	329,806	323,400
Other deferred credits and liabilities	465,878	434,367
Total Deferred Credits and Other Liabilities	1,986,534	1,913,640
Shareholders' Equity
Common stock	1	1
Other paid-in capital	2,308,211	2,308,211
Retained earnings	574,057	618,612
Accumulated other comprehensive loss	(4,409)	(4,506)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,877,860	2,922,318
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	8,558,715	8,641,145
Sierra Pacific Power Company [Member]
Current Assets:
Cash and cash equivalents	85,280	60,786
Accounts receivable less allowance for uncollectible accounts	118,326	124,464
Materials, supplies and fuel, at average cost	52,615	60,662
Intercompany income taxes receivable	10,351	10,351
Deferred income taxes	18,770	21,589
Other current assets	16,268	11,633
Total Current Assets	301,610	289,485
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	3,677,762	3,667,487
Construction work-in-progress	126,767	140,168
Total	3,804,529	3,807,655
Less accumulated provision for depreciation	1,286,870	1,277,866
Public Utilities, Property, Plant and Equipment, Net	2,517,659	2,529,789
Investments and other property, net	6,836	6,499
Other Assets, Noncurrent [Abstract]
Regulatory assets	320,432	328,755
Regulatory asset for pension plans	138,843	140,268
Other Assets, Noncurrent	11,811	21,477
Total Deferred Charges and Other Assets	471,086	490,500
Assets	3,297,191	3,316,273
Current Liabilities:
Current maturities of long-term debt	250,267	250,235
Accounts Payable	90,697	106,415
Accounts Payable, Related Parties, Current	22,387	21,534
Accrued expenses	26,464	32,936
Deferred energy	17,421	50,763
Other current liabilities	14,368	13,655
Total Current Liabilities	421,604	475,538
Long-term debt	928,851	928,990
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	473,937	465,508
Deferred investment tax credit	8,577	8,850
Accrued retirement benefits	98,956	98,676
Regulatory liabilities	228,886	227,287
Other deferred credits and liabilities	75,681	72,688
Total Deferred Credits and Other Liabilities	886,037	873,009
Shareholders' Equity
Common stock	4	4
Other paid-in capital	1,111,266	1,111,266
Retained earnings	(49,082)	(70,986)
Accumulated other comprehensive loss	(1,489)	(1,548)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,060,699	1,038,736
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,297,191	$ 3,316,273