Price Risk Management Future Year Net Unrealized Gain/Loss Recorded at Balance Sheet Date Expected to Become Realized (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
Electricity [Member]
Commodity contracts:
Other Commitment, Due in Next Twelve Months	$ 2
Other Commitment, Due in Second Year	17
Other Commitment, Due in Third Year	10
Other Commitment, Due in Fourth Year	4
Other Commitment, Due in Fifth Year	4
Other Commitment, Due after Fifth Year	39
Electricity	76
Natural Gas [Member]
Commodity contracts:
Other Commitment, Due in Next Twelve Months	4
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	8
Other Commitment, Due in Fourth Year	2
Other Commitment, Due in Fifth Year	(1)
Other Commitment, Due after Fifth Year	0
Electricity	16
Unrealized Gain Loss On Derivatives [Member]
Commodity contracts:
Other Commitment, Due in Next Twelve Months	6
Other Commitment, Due in Second Year	20
Other Commitment, Due in Third Year	18
Other Commitment, Due in Fourth Year	6
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	39
Electricity	$ 92