Risk Management and Derivative Financial Instruments (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Fair value of derivative financial instruments
Current assets	$ 53,000	$ 96,000
Total derivatives assets	180,000	287,000
Current liabilities	2,612,000	3,403,000
Non-current liabilities and deferred credits	4,362,000	3,819,000
Total derivatives liabilities	6,974,000	7,222,000
Margin deposit liabilities	0	0
Contingent Features
Margin deposit assets	5,000,000	4,200,000
Non-designated as hedging instruments due to regulatory accounting | Commodity contracts | Gas
Fair value of derivative financial instruments
Current assets	17,000	3,000
Non-current assets and deferred charges- Other		17,000
Current liabilities	10,000	104,000
Non-designated as hedging instruments due to regulatory accounting | Commodity contracts | Electric
Fair value of derivative financial instruments
Current assets	36,000	93,000
Non-current assets and deferred charges- Other	127,000	174,000
Current liabilities	2,602,000	3,299,000
Non-current liabilities and deferred credits	$ 4,362,000	$ 3,819,000