DERIVATIVES AND HEDGING ACTIVITIES (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011 MW Integer		Jun. 30, 2011 MW Integer		Dec. 31, 2010 MW
Derivative [Line Items]
Commodity volume liabilities- current (MMBTU)	3.5	[1]	3.5	[1]	18.1	[1]
Option Premiums [Line Items]
Current Assets	$ 400,000		$ 400,000		$ 1,900,000
Current Liabilities	(400,000)		(400,000)		(400,000)
Derivative Contracts
Risk management assets - current	0	[2]	0	[2]	2,100,000	[2]
Risk management liabilities - current	5,000,000	[2]	5,000,000	[2]	32,900,000	[2]
Risk management regulatory assets/liabilities - net	(5,000,000)		(5,000,000)		(30,800,000)
Gains on risk management assets, deferred to risk management regulatory assets	3,200,000		25,800,000
NPC [Member]
Derivative [Line Items]
Number of instruments held	0		0
Underlying risk			350
Aggregated notional amount	350,000,000		350,000,000
Description of hedged item			NPC's $350 million 8.25% General and Refunding Mortgage Notes, Series A, due 2011
Commodity volume liabilities- current (MMBTU)	3.0	[1]	3.0	[1]	12.9	[1]
Option Premiums [Line Items]
Current Assets	400,000		400,000		1,400,000
Current Liabilities	(400,000)		(400,000)		(400,000)
NPC [Member] | Level 2 [Member]
Derivative Contracts
Risk management assets - current					2,100,000	[2]
Risk management liabilities - current	4,100,000	[2]	4,100,000	[2]	22,400,000	[2]
Risk management regulatory assets/liabilities - net	(4,100,000)		(4,100,000)		(20,300,000)
Gains on risk management assets, deferred to risk management regulatory assets	2,600,000		16,200,000
SPPC [Member]
Derivative [Line Items]
Commodity volume liabilities- current (MMBTU)	0.5	[1]	0.5	[1]	5.2	[1]
Option Premiums [Line Items]
Current Assets					500,000
SPPC [Member] | Level 2 [Member]
Derivative Contracts
Risk management liabilities - current	900,000	[2]	900,000	[2]	10,500,000	[2]
Risk management regulatory assets/liabilities - net	(900,000)		(900,000)		(10,500,000)
Gains on risk management assets, deferred to risk management regulatory assets	$ 600,000		$ 9,600,000

[1] The change in commodity volumes at June 30, 2011, as compared to December 31, 2010, is primarily due to the suspension of the Utilities hedging program as of October 2009. As such, the Utilities exposure to mark-to-market hedging transactions has declined.

[2] When amount is negative it represents a risk management regulatory asset, when positive it represents a risk management regulatory liability. For the three months ended June 30, 2011, NVE, NPC and SPPC would have recorded cumulative gains of $3.2 million, $2.6 and $0.6 million, respectively, and for the six months ended June 30, 2011 NVE, NPC and SPPC would have recorded gains of $25.8 million, $16.2 and $9.6 million, respectively. However, as permitted by the Regulated Operations Topic of the FASB Accounting Standards Codification, NVE and the Utilities deferred these gains and losses, which are included in the risk management regulatory asset amounts above.