Commitments And Contingencies (Nuclear Fuel Agreements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Nuclear Fuel [Member]
Long-term Purchase Commitment [Line Items]
Long Term Contract For Purchase Commitments Expiration Beginning Date	2018
Long Term Contract For Purchase Commitments Expiration Ending Date	2025
Payments for Nuclear Fuel	$ 83	$ 100	$ 128
Conventional Energy [Member]
Long-term Purchase Commitment [Line Items]
Long Term Contract For Purchase Commitments Expiration Beginning Date	2018
Long Term Contract For Purchase Commitments Expiration Ending Date	2033