DEBT COVENANT AND OTHER RESTRICTIONS, Ability to Issue Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Ability to issue debt [Abstract]
Covenant terms	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 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
Maximum additional indebtedness the entity is allowed to incur under covenant	$ 2,800,000,000
NPC [Member] | Financing Authority from PUCN [Member]
Ability to issue debt [Abstract]
Maximum additional indebtedness the entity is allowed to incur under covenant	725,000,000
Maximum amount of refinancing of long-term debt securities	322,500,000
NPC [Member] | Financing Authority from PUCN [Member] | Revolving Credit Facility [Member]
Ability to issue debt [Abstract]
Maximum amount of credit facility the entity has authority to maintain	1,300,000,000
NPC [Member] | Financial Covenants Within Financing Agreements [Member] | Revolving Credit Facility [Member]
Ability to issue debt [Abstract]
Covenant terms	ratio of consolidated indebtedness to consolidated capital, determined as of the last day of each fiscal quarter, not to exceed 0.68 to 1
Maximum additional indebtedness the entity is allowed to incur under covenant	2,600,000,000
Maximum amount of credit facility the entity has authority to maintain	600,000,000
NPC [Member] | Indenture [Member] | General and Refunding Mortgage Securities [Member]
Ability to issue debt [Abstract]
Maximum additional indebtedness the entity is allowed to incur under covenant	1,400,000,000
Amount of secured debt outstanding	4,100,000,000
Percent of net utility property additions on which capacity to issue additional debt is based (in hundredths)	70.00%
SPPC [Member] | Financing Authority from PUCN [Member]
Ability to issue debt [Abstract]
Maximum additional indebtedness the entity is allowed to incur under covenant	350,000,000
Maximum amount of refinancing of long-term debt securities	348,000,000
SPPC [Member] | Financing Authority from PUCN [Member] | Revolving Credit Facility [Member]
Ability to issue debt [Abstract]
Maximum amount of credit facility the entity has authority to maintain	600,000,000
SPPC [Member] | Financial Covenants Within Financing Agreements [Member] | Revolving Credit Facility [Member]
Ability to issue debt [Abstract]
Covenant terms	ratio of consolidated indebtedness to consolidated capital, determined as of the last day of each fiscal quarter, not to exceed 0.68 to 1
Maximum additional indebtedness the entity is allowed to incur under covenant	879,000,000
Maximum amount of credit facility the entity has authority to maintain	250,000,000
SPPC [Member] | Indenture [Member] | General and Refunding Mortgage Securities [Member]
Ability to issue debt [Abstract]
Maximum additional indebtedness the entity is allowed to incur under covenant	760,300,000
Amount of secured debt outstanding	$ 1,500,000,000
Percent of net utility property additions on which capacity to issue additional debt is based (in hundredths)	70.00%