STOCK COMPENSATION PLANS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of authorized shares (in shares)	7,750,000
Total Stock Compensation Expense	$ 25,530	$ 19,001	$ 8,494
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense			71
Terms of award	These grants are at 100% of the then current fair market value, and vest over different periods as stated in the grant. These options have to be exercised within ten years of award, and no earlier than one year from the date of grant. At the time of grant, rights to dividend equivalents may be awarded; however, historically, dividend equivalents have not been granted. The options may be exercised using either cash or previously acquired shares valued at the current market price, or a combination of both. The Committee also allows cashless exercises, subject to applicable securities law restrictions or other means consistent with the purpose of the plan and the applicable law.
Performance Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	21,684	16,523	7,145
Terms of award	Performance Units vest at the end of a three-year period to the extent that specific stock price related performance targets are met, as determined by the Compensation Committee. If the established objectives are not met, the Performance Units are forfeited. Performance Units are typically paid in shares after vesting. At the time of grant, rights to dividend equivalents may be awarded; however, historically, dividend equivalents have not been granted. These awards do not have any voting rights associated with them. Performance Units granted are measured based on NVE's TSR relative to the average TSR of companies listed in the S&P Super Composite Electric Utility Index throughout the three-year performance period. Performance Shares vest at the end of a three-year period, based on average aggregate Corporate Goal performance under the Short Term Incentive Plan (STIP) and the average STIP payout over those three years. If the established objectives are not met, the Performance Shares are forfeited. Performance Shares are paid in shares, minus applicable taxes, based on the then fair market value of the shares. At the time of grant, rights to dividend equivalents may be awarded; however, historically, dividend equivalents have not been granted. Performance shares do not have any voting rights associated with them.
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	3,552	2,151	902
Terms of award	These grants vest over different periods as stated within the terms of each grant. The issuance of these shares is conditional upon the employee retaining employment with NVE throughout the entire vesting period.
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of authorized shares (in shares)	1,900,162
Total Stock Compensation Expense	294	327	376
Terms of award	According to the terms of the plan, employees can choose twice each year to have up to 15% of their base earnings withheld to purchase NVE's common stock. The option price discount is 15%, and the purchase price is the lesser of 85% of the market value on the offering commencement date, or 85% of the market value on the offering exercise date. Employees can withdraw from the plan at any time prior to the exercise date.
Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract]
Additional shares authorized for employee stock purchase plan (in shares)	1,000,000
Number of shares sold to employees (in shares)	134,069	134,266	147,457
NVE [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	360	216	93
NVE [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense			1
NVE [Member] | Performance Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	277	163	54
NVE [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	74	35	10
NVE [Member] | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	9	18	28
Nevada Power Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	17,680	12,145	5,761
Nevada Power Company [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense			51
Nevada Power Company [Member] | Performance Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	14,967	10,438	4,966
Nevada Power Company [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	2,501	1,492	610
Nevada Power Company [Member] | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	212	215	134
Sierra Pacific Power Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	7,490	6,640	2,640
Sierra Pacific Power Company [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense			19
Sierra Pacific Power Company [Member] | Performance Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	6,440	5,922	2,125
Sierra Pacific Power Company [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	977	624	282
Sierra Pacific Power Company [Member] | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock Compensation Expense	$ 73	$ 94	$ 214