LONG-TERM DEBT, Debt Instruments (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	$ (759,000)	$ (1,631,000)
Current maturities	(129,457,000)	(356,283,000)
Total Long-Term Debt	4,791,809,000	4,669,798,000
Secured, General and Refunding Mortgage Securities, NPC Series L [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	250,000,000
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	210,000,000	210,000,000
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	370,000,000	370,000,000
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	325,000,000	325,000,000
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	350,000,000	350,000,000
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	500,000,000	500,000,000
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	125,000,000	125,000,000
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	500,000,000	500,000,000
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	250,000,000	250,000,000
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	250,000,000	250,000,000
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	450,000,000	450,000,000
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	251,742,000	251,742,000
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	0	250,000,000
Stated interest rate (in hundredths)	5.45%
Maturity date	2013
General and Refunding Mortgage Securities SPPC Series T [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	0
Stated interest rate (in hundredths)	3.375%
Maturity date	2023
Secured Variable Rate Debt Npc Idrb Series Two Thousand [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities		98,100,000
Maturity date	2020
Secured Variable Rate Debt, NPC PCRB Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,700,000	37,700,000
Maturity date	2036
Secured Variable Rate Debt Npc Pcrb Series Two Thousand Six [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,975,000	37,975,000
Maturity date	2032
Secured Variable Rate Debt Sppc Pcrb Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	58,200,000	58,200,000
Maturity date	2031
Secured Variable Rate Debt Sppc Pcrb Series 2006 B [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	75,000,000	75,000,000
Maturity date	2036
Secured Variable Rate Debt Sppc Pcrb Series 2006 C [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	81,475,000	81,475,000
Maturity date	2036
NVE Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	195,000,000	195,000,000
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	315,000,000	315,000,000
Stated interest rate (in hundredths)	6.25%
Maturity date	2020
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	38,415,000	44,258,000
Parent Company
Debt Instrument [Line Items]
Total Long-Term Debt	510,000,000	510,000,000
Parent Company | NVE Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	195,000,000	195,000,000
Parent Company | NVE Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	315,000,000	315,000,000
Nevada Power Company
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	9,080,000	9,827,000
Current maturities	(129,186,000)	(106,048,000)
Total Long-Term Debt	3,103,980,000	3,230,808,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series L [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	250,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	210,000,000	210,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series N [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	370,000,000	370,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series O [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	325,000,000	325,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series R [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	350,000,000	350,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, NPC Series S [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000,000	500,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, Series U [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	125,000,000	125,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, Series V [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	500,000,000	500,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, Series X [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	250,000,000
Nevada Power Company | Secured, General and Refunding Mortgage Securities, Series Y [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	250,000,000
Nevada Power Company | Secured Variable Rate Debt Npc Idrb Series Two Thousand [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities		98,100,000
Notice Of Redemption	100,000,000
Notice Of Redemption Date	July 1, 2013
Redemption Date	August 1, 2013
Redemption Percentage	100.00%
Amount of debt redeemed	98,100,000
Nevada Power Company | Secured Variable Rate Debt, NPC PCRB Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,700,000	37,700,000
Nevada Power Company | Secured Variable Rate Debt Npc Pcrb Series Two Thousand Six [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	37,975,000	37,975,000
Nevada Power Company | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	36,571,000	42,908,000
Sierra Pacific Power Company
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium), Net	(9,839,000)	(11,458,000)
Current maturities	(271,000)	(250,235,000)
Total Long-Term Debt	1,177,829,000	928,990,000
Sierra Pacific Power Company | Secured, General and Refunding Mortgage Securities, SPPC Series M [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	450,000,000	450,000,000
Sierra Pacific Power Company | Secured, General and Refunding Mortgage Securities, SPPC Series P [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	251,742,000	251,742,000
Sierra Pacific Power Company | Secured, General and Refunding Mortgage Securities, SPPC Series Q [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	0	250,000,000
Redemption Date	September 1, 2013
Amount of debt redeemed	250,000,000
Sierra Pacific Power Company | General and Refunding Mortgage Securities SPPC Series T [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	250,000,000	0
Net Proceeds used to redeem debt	247,900,000
Debt Instrument, Issuance Date	Aug. 01, 2013
Sierra Pacific Power Company | Secured Variable Rate Debt Sppc Pcrb Series 2006 [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	58,200,000	58,200,000
Sierra Pacific Power Company | Secured Variable Rate Debt Sppc Pcrb Series 2006 B [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	75,000,000	75,000,000
Sierra Pacific Power Company | Secured Variable Rate Debt Sppc Pcrb Series 2006 C [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	81,475,000	81,475,000
Sierra Pacific Power Company | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Long-term debt including current maturities	$ 1,844,000	$ 1,350,000