CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 261,068	$ 298,271
Accounts receivable less allowance for uncollectible accounts	433,336	373,099
Materials, supplies and fuel, at average cost	130,747	138,337
Deferred energy costs - electric	30,122	0
Deferred energy costs - gas	991	0
Deferred income taxes	109,450	60,592
Other current assets	47,591	40,750
Total Current Assets	1,013,305	911,049
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	12,159,227	12,031,053
Construction work-in-progress	757,924	708,109
Total	12,917,151	12,739,162
Less accumulated provision for depreciation	3,448,469	3,313,188
Public Utilities, Property, Plant and Equipment, Net	9,468,682	9,425,974
Investments and other property, net	63,387	56,660
Other Assets, Noncurrent [Abstract]
Deferred energy	81,274	87,072
Regulatory assets	1,077,364	1,132,768
Regulatory asset for pension plans	274,200	281,195
Other Assets, Noncurrent	75,029	89,418
Total Deferred Charges and Other Assets	1,507,867	1,590,453
Assets	12,053,241	11,984,136
Current Liabilities:
Current maturities of long-term debt	480,018	356,283
Accounts Payable	333,588	332,245
Accrued expenses	119,245	127,693
Deferred energy	0	136,865
Other current liabilities	69,895	66,221
Total Current Liabilities	1,002,746	1,019,307
Long-term debt	4,543,733	4,669,798
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,564,260	1,470,973
Deferred investment tax credit	12,430	13,538
Accrued retirement benefits	167,793	162,260
Regulatory liabilities	583,217	550,687
Other deferred credits and liabilities	614,873	540,202
Total Deferred Credits and Other Liabilities	2,942,573	2,737,660
Shareholders' Equity
Common stock	236,000	236,000
Treasury stock, at cost	(8,542)	(16,804)
Other paid-in capital	2,715,358	2,712,943
Retained earnings	630,521	635,303
Accumulated other comprehensive loss	(9,148)	(10,071)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	3,564,189	3,557,371
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	12,053,241	11,984,136
Nevada Power Company [Member]
Current Assets:
Cash and cash equivalents	141,686	201,202
Accounts receivable less allowance for uncollectible accounts	323,870	248,501
Materials, supplies and fuel, at average cost	77,488	77,675
Deferred energy costs - electric	27,389	0
Deferred income taxes	86,367	48,590
Other current assets	35,102	28,763
Total Current Assets	691,902	604,731
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	8,437,303	8,363,566
Construction work-in-progress	649,128	567,941
Total	9,086,431	8,931,507
Less accumulated provision for depreciation	2,143,914	2,035,322
Public Utilities, Property, Plant and Equipment, Net	6,942,517	6,896,185
Investments and other property, net	50,027	49,808
Other Assets, Noncurrent [Abstract]
Deferred energy	80,109	87,072
Regulatory assets	762,681	804,013
Regulatory asset for pension plans	133,409	136,682
Other Assets, Noncurrent	58,959	62,654
Total Deferred Charges and Other Assets	1,035,158	1,090,421
Assets	8,719,604	8,641,145
Current Liabilities:
Current maturities of long-term debt	229,743	106,048
Accounts Payable	212,133	201,193
Accounts Payable, Related Parties, Current	48,398	42,036
Accrued expenses	82,199	86,433
Deferred energy	0	86,102
Other current liabilities	55,326	52,567
Total Current Liabilities	627,799	574,379
Long-term debt	3,104,936	3,230,808
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	1,173,431	1,101,804
Deferred investment tax credit	4,126	4,688
Accrued retirement benefits	51,418	49,381
Regulatory liabilities	343,521	323,400
Other deferred credits and liabilities	507,751	434,367
Total Deferred Credits and Other Liabilities	2,080,247	1,913,640
Shareholders' Equity
Common stock	1	1
Other paid-in capital	2,308,211	2,308,211
Retained earnings	602,722	618,612
Accumulated other comprehensive loss	(4,312)	(4,506)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	2,906,622	2,922,318
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	8,719,604	8,641,145
Sierra Pacific Power Company [Member]
Current Assets:
Cash and cash equivalents	91,950	60,786
Accounts receivable less allowance for uncollectible accounts	109,324	124,464
Materials, supplies and fuel, at average cost	53,259	60,662
Deferred energy costs - electric	2,733	0
Deferred energy costs - gas	991	0
Intercompany income taxes receivable	10,351	10,351
Deferred income taxes	33,190	21,589
Other current assets	11,799	11,633
Total Current Assets	313,597	289,485
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Plant in service	3,721,924	3,667,487
Construction work-in-progress	108,796	140,168
Total	3,830,720	3,807,655
Less accumulated provision for depreciation	1,304,555	1,277,866
Public Utilities, Property, Plant and Equipment, Net	2,526,165	2,529,789
Investments and other property, net	6,792	6,499
Other Assets, Noncurrent [Abstract]
Deferred energy	1,165	0
Regulatory assets	314,683	328,755
Regulatory asset for pension plans	137,050	140,268
Other Assets, Noncurrent	10,790	21,477
Total Deferred Charges and Other Assets	463,688	490,500
Assets	3,310,242	3,316,273
Current Liabilities:
Current maturities of long-term debt	250,275	250,235
Accounts Payable	85,323	106,415
Accounts Payable, Related Parties, Current	28,209	21,534
Accrued expenses	30,990	32,936
Deferred energy	0	50,763
Other current liabilities	14,570	13,655
Total Current Liabilities	409,367	475,538
Long-term debt	928,797	928,990
Commitments and Contingencies
Deferred Credits and Other Liabilities:
Deferred income taxes	492,443	465,508
Deferred investment tax credit	8,304	8,850
Accrued retirement benefits	99,732	98,676
Regulatory liabilities	239,696	227,287
Other deferred credits and liabilities	80,370	72,688
Total Deferred Credits and Other Liabilities	920,545	873,009
Shareholders' Equity
Common stock	4	4
Other paid-in capital	1,111,266	1,111,266
Retained earnings	(58,306)	(70,986)
Accumulated other comprehensive loss	(1,431)	(1,548)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,051,533	1,038,736
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 3,310,242	$ 3,316,273