Fair Value of Financial Instruments (Details-3)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Basis adjustment:
Basis adjustment - on peak	96.90%	98.10%
Basis adjustment - off peak	95.10%	95.00%
US Treasury Bills [Member]
Deferred compensation plan
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:
Internal generation	60.00%	50.00%
Purchased power	25.00%	30.00%
Maximum [Member]
Counterparty fuel mix:
Internal generation	75.00%	70.00%
Purchased power	40.00%	50.00%