Long-Term Debt (Details Textuals) (Electric [Member], USD $) In Millions, unless otherwise specified					1 Months Ended
	Jun. 30, 2014 Tax Exempt Revenue Bonds [Member]	Apr. 30, 2014 Tax Exempt Revenue Bonds [Member]	Jun. 30, 2014 Final Maturity of 2025 [Member] Mortgages [Member]	Jun. 30, 2014 Final Maturity of 2044 [Member] Mortgages [Member]	Jun. 30, 2014 Final Maturity of 2015 [Member] Senior Notes [Member]	Jun. 30, 2014 Final Maturity of 2029 [Member] Tax Exempt Revenue Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount, Future Issuance			$ 350	$ 350
Future Debt Instrument, Interest Rate, Stated Percentage			3.375%	4.30%
Future Extinguishment of Debt, Amount					$ 200	$ 60
Debt Instrument, Interest Rate, Stated Percentage	4.875%	2.35%			4.80%	5.25%