LONG-TERM DEBT, Financing Transactions (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Transactions [Abstract]
Net proceeds from issuance	$ 130,485,000	$ 579,820,000	$ 985,419,000
Secured, General and Refunding Mortgage Securities, NPC Series I [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)		6.50%
Maturity date		2012
Secured, General and Refunding Mortgage Securities, Series X [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	5.375%
Maturity date	2040
Secured, General and Refunding Mortgage Securities, Series Y [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	5.45%
Maturity date	2041
NVE Senior Notes due 2014 [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	2.81%
Maturity date	2014
NVE Senior Notes due 2020 [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	6.25%
Maturity date	2020
Parent Company [Member] | Term Loan [Member]
Financing Transactions [Abstract]
Issuance date		Oct. 01, 2011
Face amount		195,000,000
Duration of loan agreement (in years)		3
Maturity date		October 7, 2014
Effective interest rate (in hundredths)		2.81%
Covenant description		(i) a financial covenant to maintain a ratio of total consolidated indebtedness to total consolidated capitalization, determined on the last day of each fiscal quarter, not to exceed 0.70 to 1.00 and (ii) a fixed charge covenant that requires NVE not to permit the fixed charge coverage ratio, determined on the last day of each fiscal quarter, to be less than 1.50 to 1.00
LIBOR rate margin (in hundredths)		2.00%
Parent Company [Member] | NVE Senior Notes due 2017 [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)		6.75%
Redemption notice date		November 2011
Percentage of stated principal amount plus accrued interest at which Notes will be redeemed (in hundredths)		102.25%
Debt redeemed		191,500,000
Parent Company [Member] | Swap [Member]
Financing Transactions [Abstract]
DerivativeUnderlyingRisk		interest rate
DerivativeFixedInterestRate		2.81%
DerivativeDescriptionOfHedgedItem		3-year term loan
Nevada Power Company [Member]
Financing Transactions [Abstract]
Net proceeds from issuance	132,259,000	386,884,000	637,463,000
Nevada Power Company [Member] | Secured General And Refunding Mortgage Securities Npc Series [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	8.25%
Maturity date		June 1, 2011
Debt redeemed	350,000,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, NPC Series I [Member]
Financing Transactions [Abstract]
Stated interest rate (in hundredths)	6.50%
Redemption notice date	April 2012
Debt redeemed	130,000,000
Cash used to pay down debt	10,000,000
draw on credit facility	120,000,000
Nevada Power Company [Member] | Secured, General and Refunding Mortgage Securities, Series Y [Member]
Financing Transactions [Abstract]
Issuance date	May 01, 2011
Stated interest rate (in hundredths)	5.45%
Face amount	250,000,000
Maturity date	May 15, 2041
Net proceeds from issuance	248,000,000
Proceeds from issuance used to redeem other debt	248,000,000
Swap transaction settlement date		May 9, 2011
Settlement payment amount		14,900,000
Amortization period of regulatory asset established upon settlement of swap transaction (in years)		30
Nevada Power Company [Member] | Swap [Member]
Financing Transactions [Abstract]
Notional amount of interest rate swap		250,000,000
DerivativeUnderlyingRisk		interest rate
DerivativeDescriptionOfHedgedItem		$350 million aggregate principal amount of 8.25% General and Refunding Mortgage Notes, Series A, which matured on June 1, 2011
Nevada Power Company [Member] | revolving credit facility
Financing Transactions [Abstract]
Credit facility maximum borrowing capacity	500,000,000
Credit facility expiration date	Mar. 01, 2017
Credit facility interest rate description	an applicable base rate (defined as the highest of the Prime Rate, the Federal Funds Rate plus 0.5% and the LIBOR Base Rate plus 1.0%) plus a margin, or a LIBOR rate plus a margin
Base rate margin (in hundredths)	0.25%
LIBOR rate margin (in hundredths)	1.25%
Maximum percentage of total commitments in effect that limits reduction in availability (in hundredths)	50.00%
Negative mark-to-market exposure	0
Covenant terms	maintain a ratio of consolidated indebtedness to consolidated capital, determined as of the last day of each fiscal quarter, not to exceed 0.68 to 1.00
Nevada Power Company [Member] | Terminated Revolving Credit Facility [Member]
Financing Transactions [Abstract]
Credit facility maximum borrowing capacity	600,000,000
Credit facility termination date	March 2012
Credit facility expiration date	Apr. 01, 2013
Sierra Pacific Power Company [Member]
Financing Transactions [Abstract]
Net proceeds from issuance	(1,727,000)	(403,000)	37,726,000
Sierra Pacific Power Company [Member] | revolving credit facility
Financing Transactions [Abstract]
Credit facility maximum borrowing capacity	250,000,000
Credit facility expiration date	Mar. 01, 2017
Credit facility interest rate description	an applicable base rate (defined as the highest of the Prime Rate, the Federal Funds Rate plus 0.5% and the LIBOR Base Rate plus 1.0%) plus a margin, or a LIBOR rate plus a margin
Base rate margin (in hundredths)	0.25%
LIBOR rate margin (in hundredths)	1.25%
Maximum percentage of total commitments in effect that limits reduction in availability (in hundredths)	50.00%
Negative mark-to-market exposure	0
Covenant terms	maintain a ratio of consolidated indebtedness to consolidated capital, determined as of the last day of each fiscal quarter, not to exceed 0.68 to 1.00
Sierra Pacific Power Company [Member] | Terminated Revolving Credit Facility [Member]
Financing Transactions [Abstract]
Credit facility maximum borrowing capacity	$ 250,000,000
Credit facility termination date	March 2012
Credit facility expiration date	Apr. 01, 2013