Derivative and Hedging Instruments (Details-1) (USD $)	Dec. 31, 2011 MW MWh Dth	Dec. 31, 2010 MWh Dth MW
Gross Notional Volume of Open Derivatives [Abstract]
Commodity derivative contracts - MWh	482,545	544,820
Commodity derivative contracts - Dth	4,030,000	5,420,000
Financial transmission rights - MW	2,382	2,609
Derivative collateral [Abstract]
Derivative collateral	$ 3,000,000	$ 500,000
Derivative Fair Values [Abstract]
Exchange traded and financial transmission rights	(2,800,000)	(200,000)
Purchased power agreement	(39,500,000)	(19,000,000)
Commodity Derivative Contracts [Member]
Derivative instruments at fair value on the balance sheet [Line Items]
Other current assets	177,000	649,000
Other defered charges	92,000	214,000
Other current liabilities	3,060,000	1,227,000
Other deferred liabilities	231,000	167,000
Financial Transmission Rights [Member]
Derivative instruments at fair value on the balance sheet [Line Items]
Other current assets	186,000	312,000
Other current liabilities	0	0
Purchased Power Agreement [Member]
Derivative instruments at fair value on the balance sheet [Line Items]
Other current liabilities	4,600,000
Other deferred liabilities	$ 34,920,000	$ 19,010,000