REGULATORY MATTERS (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010
Bad Debt Rider [Abstract]
Description of order issued	Bad debt rider.
Net recovery related to 2008 and 2009 bad debt experience over benchmark		$ 31.7
Benchmark of the net bad debt rider recovery from customers			63	63
Bad debt experience				35.7
Amount of net bad debt rider (recovery from) refund to customers				$ 27.3
Substitute Natural Gas: Contract 1 [Abstract]
Volume Of Substitute Natural Gas (in Bcf): Contract 1	25
Capacity Of Coal Gasification Plant (in Bcf): Contract 1	60
Term (in years): Contract 1	10-year
Substitute Natural Gas: Contract 2 [Abstract]
Volume of Substitute Natual Gas (in Bcf): Contract 2	20
Term (in years): Contract 2	30-year