Derivative and Hedging Instruments (Details-1) (USD $)	Sep. 30, 2013 MW MWh Dth	Dec. 31, 2012 MWh Dth MW
Gross notional volume of open derivatives [Abstract]
Commodity derivative contracts - MWh	300,195	444,650
Commodity derivative contracts - Dth	5,970,000	1,980,000
Financial transmission rights - MW	3,099	2,670
Derivative fair values [Abstract]
Exchange traded and financial transmission rights	$ 900,000	$ 300,000
Purchased power agreement	(69,000,000)	(72,600,000)
Derivatives Fair Value [Line Items]
Derivative liability (current)	9,310,000	9,270,000
Derivative liability (long-term)	59,710,000	63,320,000
Commodity Derivative Contracts [Member]
Derivatives Fair Value [Line Items]
Other current assets	608,000	365,000
Other defered charges	32,000	95,000
Derivative liability (current)	213,000	394,000
Derivative liability (long-term)	18,000	11,000
Offsetting Assets [Line Items]
Gross amounts	640,000	460,000
Gross amounts offset in balance sheet	(231,000)	(405,000)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	409,000	55,000
Financial Transmission Rights [Member]
Derivatives Fair Value [Line Items]
Other current assets	528,000	206,000
Derivative liability (current)	0	0
Offsetting Assets [Line Items]
Gross amounts	528,000	206,000
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	528,000	206,000
Purchased Power Agreement [Member]
Derivatives Fair Value [Line Items]
Derivative liability (current)	9,310,000	9,270,000
Derivative liability (long-term)	$ 59,710,000	$ 63,320,000