Derivative and Hedging Instruments (Details-1) (USD $)	Jun. 30, 2011 MW Tons Dth MWh	Dec. 31, 2010 MWh Dth MW
Gross Notional Volume of Open Derivatives [Abstract]
Commodity derivative contracts - MWh	550,475	544,820
Commodity derivative contracts - Dth	5,000,000	5,420,000
Financial transmission rights - MW	5,088	2,609
Derivative Collateral [Abstract]
Derivative collateral	$ 0	$ 500,000
Derivative Fair Values [Abstract]
Exchange traded and financial transmission rights	1,000,000	(200,000)
Purchased power agreement	(23,600,000)	(19,000,000)
Commodity Contract [Member]
Derivative instruments at fair value on the balance sheet [Line Items]
Other current assets	1,285,000	649,000
Other defered charges	72,000	214,000
Other current liabilities	558,000	1,227,000
Other deferred liabilities	27,000	167,000
Financial Transmission Rights [Member]
Derivative instruments at fair value on the balance sheet [Line Items]
Other current assets	229,000	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	725,000	0
Other deferred liabilities	$ 22,880,000	$ 19,010,000