LONG-TERM DEBT, Debt Instruments (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	$ (1,405)	$ (1,631)
Current maturities	(480,018,000)	(356,283,000)
Total Long-Term Debt	4,543,733,000	4,669,798,000
Secured, General and Refunding Mortgage Securities, NPC Series L [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Stated interest rate (in hundredths)	5.875%
Maturity date	2015
Secured, General and Refunding Mortgage Securities, NPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	210,000	210,000
Stated interest rate (in hundredths)	5.95%
Maturity date	2016
Secured, General and Refunding Mortgage Securities, NPC Series N [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	370,000	370,000
Stated interest rate (in hundredths)	6.65%
Maturity date	2036
Secured, General and Refunding Mortgage Securities, NPC Series O [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	325,000	325,000
Stated interest rate (in hundredths)	6.50%
Maturity date	2018
Secured, General and Refunding Mortgage Securities, NPC Series R [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	350,000	350,000
Stated interest rate (in hundredths)	6.75%
Maturity date	2037
Secured, General and Refunding Mortgage Securities, NPC Series S [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000	500,000
Stated interest rate (in hundredths)	6.50%
Maturity date	2018
Secured, General and Refunding Mortgage Securities, Series U [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	125,000	125,000
Stated interest rate (in hundredths)	7.375%
Maturity date	2014
Secured, General and Refunding Mortgage Securities, Series V [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000	500,000
Stated interest rate (in hundredths)	7.125%
Maturity date	2019
Secured, General and Refunding Mortgage Securities, Series X [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Stated interest rate (in hundredths)	5.375%
Maturity date	2040
Secured, General and Refunding Mortgage Securities, Series Y [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Stated interest rate (in hundredths)	5.45%
Maturity date	2041
Secured, General and Refunding Mortgage Securities, SPPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	450,000	450,000
Stated interest rate (in hundredths)	6.00%
Maturity date	2016
Secured, General and Refunding Mortgage Securities, SPPC Series P [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	251,742	251,742
Stated interest rate (in hundredths)	6.75%
Maturity date	2037
Secured, General and Refunding Mortgage Securities, SPPC Series Q [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Stated interest rate (in hundredths)	5.45%
Maturity date	2013
Secured Variable Rate Debt Npc Idrb Series Two Thousand [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	98,100	98,100
Maturity date	2020
Secured Variable Rate Debt, NPC PCRB Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,700	37,700
Maturity date	2036
Secured Variable Rate Debt Npc Pcrb Series Two Thousand Six [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,975	37,975
Maturity date	2032
Secured Variable Rate Debt Sppc Pcrb Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	58,200	58,200
Maturity date	2031
Secured Variable Rate Debt Sppc Pcrb Series 2006 B [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	75,000	75,000
Maturity date	2036
Secured Variable Rate Debt Sppc Pcrb Series 2006 C [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	81,475	81,475
Maturity date	2036
NVE Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	195,000	195,000
Stated interest rate (in hundredths)	2.56%
Maturity date	2014
NVE Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	315,000	315,000
Stated interest rate (in hundredths)	6.25%
Maturity date	2020
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	42,154	44,258
Parent Company [Member] | NVE Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	195,000	195,000
Parent Company [Member] | NVE Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	315,000	315,000
Nevada Power Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	9,329	9,827
Current maturities	(229,743,000)	(106,048,000)
Total Long-Term Debt	3,104,936,000	3,230,808,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series L [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	210,000	210,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series N [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	370,000	370,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series O [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	325,000	325,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series R [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	350,000	350,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series S [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000	500,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, Series U [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	125,000	125,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, Series V [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000	500,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, Series X [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, Series Y [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Nevada Power Company [Member] | Secured Variable Rate Debt Npc Idrb Series Two Thousand [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	98,100	98,100
Notice Of Redemption	100,000,000
Notice Of Redemption Date	July 2, 2013
Redemption Date	August 21, 2013
Redemption Percentage	100.00%
Nevada Power Company [Member] | Secured Variable Rate Debt, NPC PCRB Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,700	37,700
Nevada Power Company [Member] | Secured Variable Rate Debt Npc Pcrb Series Two Thousand Six [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,975	37,975
Nevada Power Company [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	40,233	42,908
Sierra Pacific Power Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	(10,734)	(11,458)
Current maturities	(250,275,000)	(250,235,000)
Total Long-Term Debt	928,797,000	928,990,000
Sierra Pacific Power Company [Member] | Secured, General and Refunding Mortgage Securities, SPPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	450,000	450,000
Sierra Pacific Power Company [Member] | Secured, General and Refunding Mortgage Securities, SPPC Series P [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	251,742	251,742
Sierra Pacific Power Company [Member] | Secured, General and Refunding Mortgage Securities, SPPC Series Q [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000	250,000
Sierra Pacific Power Company [Member] | Secured Variable Rate Debt Sppc Pcrb Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	58,200	58,200
Sierra Pacific Power Company [Member] | Secured Variable Rate Debt Sppc Pcrb Series 2006 B [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	75,000	75,000
Sierra Pacific Power Company [Member] | Secured Variable Rate Debt Sppc Pcrb Series 2006 C [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	81,475	81,475
Sierra Pacific Power Company [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 1,921	$ 1,350