Fair Value of Financial Instruments (Details-3)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value Inputs Assets Quantitative Information [Line Items]
Basis adjustment - on peak	97.40%	98.10%
Basis adjustment - off peak	95.40%	95.00%
US Treasury Bill Securities [Member]
Deferred compensation plan [Abstract]
Investment interest calculation, investment maturity period (26 weeks)	182 days
Investment interest calculation, monthly compounding rate	1.00%
Investment interest calculation, minimum annual rate compounded monthly	7.00%
Minimum [Member]
Counterparty fuel mix [Abstract]
Internal generation	60.00%	50.00%
Purchased power	40.00%	50.00%
Maximum [Member]
Counterparty fuel mix [Abstract]
Internal generation	75.00%	70.00%
Purchased power	25.00%	30.00%