Risk Management and Derivative Financial Instruments (Details 2) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Electric
Gain / (Loss) on derivatives
Unrealized losses applicable to financial instruments which will settle in next twelve months	$ 2,600,000		$ 2,600,000		$ 2,600,000
Period within which financial instruments will settle			12 months
Amount of Gain/(Loss) Recognized on Balance Sheet	(2,852,000)	474,000	(432,000)	(1,828,000)	(1,052,000)	(8,057,000)
Amount of Gain / (Loss) Recognized in Income on Derivative	(407,000)	83,000	(521,000)	59,000	(4,565,000)	(1,781,000)
Gas
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	(71,000)	164,000	(18,000)	(491,000)	12,000	(2,136,000)
Commodity contracts | Electric
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	(2,852,000)	474,000	(432,000)	(1,828,000)	(1,052,000)	(8,057,000)
Amount of Gain / (Loss) Recognized in Income on Derivative	(407,000)	83,000	(521,000)	59,000	(4,565,000)	(1,781,000)
Commodity contracts | Gas
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	$ (71,000)	$ 164,000	$ (18,000)	$ (491,000)	$ 12,000	$ (2,136,000)