Risk Management and Derivative Financial Instruments (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Electric
Gain / (Loss) on derivatives
Unrealized losses applicable to financial instruments which will settle in next twelve months	$ 1,100,000		$ 1,100,000
Period within which financial instruments will settle	12 months
Amount of Gain/(Loss) Recognized on Balance Sheet	2,421,000	(2,302,000)	(2,275,000)	(9,899,000)
Amount of Gain / (Loss) Recognized in Income on Derivative	(114,000)	(24,000)	(4,075,000)	(2,416,000)
Gas
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	95,000	(655,000)	289,000	(2,475,000)
Commodity contracts | Electric
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	2,421,000	(2,302,000)	(2,275,000)	(9,899,000)
Amount of Gain / (Loss) Recognized in Income on Derivative	(114,000)	(24,000)	(4,075,000)	(2,416,000)
Commodity contracts | Gas
Gain / (Loss) on derivatives
Amount of Gain/(Loss) Recognized on Balance Sheet	$ 95,000	$ (655,000)	$ 289,000	$ (2,475,000)