INVESTMENTS IN SUBSIDIARIES AND OTHER PROPERTY (Details) (USD $)	Dec. 31, 2011		Dec. 31, 2010
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	$ 29,182,000	[1]	$ 29,348,000	[1]
Cash Value-Life Insurance	2,735,000		2,646,000
Non-utility property of NEICO	5,517,000		5,659,000
Non-utility property of SPC	0
Property not designated for Utility use	19,235,000		23,608,000
Other non-utility property	352,000		352,000
Total investments and other property	57,021,000		61,613,000
Cash surrender value of life insurance policies	13,500,000
NPC [Member]
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	23,675,000	[2]	23,810,000	[2]
Cash Value-Life Insurance	2,735,000		2,646,000
Non-utility property of NEICO	5,517,000		5,659,000
Property not designated for Utility use	18,841,000		23,190,000
Total investments and other property	50,768,000		55,305,000
SPPC [Member]
Investments in subsidiaries and other property [Line Items]
Investments held in Rabbi Trust	5,507,000	[2]	5,538,000	[2]
Property not designated for Utility use	394,000		418,000
Total investments and other property	$ 5,901,000		$ 5,956,000

[1] Amounts recognized as non-current liabilities (accrued retirement benefits) in the consolidated balance sheets as of December 31, 2011 and 2010.

[2] Rabbi Trust assets represent non-qualified deferred compensation and certain defined benefit plans, which consist of actively traded money market and equity funds with quoted prices in active markets which are considered level 1 in the fair value hierarchy. The balance also includes life insurance policies, which are recorded at its cash surrender value of $13.5 million on the consolidated balance sheet, which are considered level 2 in the fair value hierarchy.