REGULATORY ACTIONS, Summary of Regulatory Actions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
NPC [Member]
Summary of Rate Filings [Line Items]
Amount Of Apportionment Sought	$ 14
Gain on Sale of Telecommunications Towers	32
Revenue Requirement Subject To Change:
Requested and Amended Revenue Requirement	56.6
Present Revenue Requirement	26.5
$ Change in Revenue Requirement	30.1
NPC [Member] | DEAA [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Requested and Amended Revenue Requirement	13.1
Present Revenue Requirement	0
$ Change in Revenue Requirement	13.1
NPC [Member] | REPR [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Requested and Amended Revenue Requirement	28.2
Present Revenue Requirement	8.5
$ Change in Revenue Requirement	19.7
NPC [Member] | TRED [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Requested and Amended Revenue Requirement	15.3
Present Revenue Requirement	18.0
$ Change in Revenue Requirement	(2.7)
SPPC [Member] | SPPC Electric [Member]
Revenue Requirement Subject To Change:
Requested and Amended Revenue Requirement	40.6
Present Revenue Requirement	47.7
$ Change in Revenue Requirement	(7.1)
SPPC [Member] | SPPC Electric [Member] | REPR [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Requested and Amended Revenue Requirement	34.5
Present Revenue Requirement	38.5
$ Change in Revenue Requirement	(4.0)
SPPC [Member] | SPPC Electric [Member] | TRED [Member]
Revenue Requirement Subject To Change:
Anticipated Effective Date	Oct. 2012
Requested and Amended Revenue Requirement	6.1
Present Revenue Requirement	9.2
$ Change in Revenue Requirement	$ (3.1)