Financial Risk Management Activities (Schedule Of Derivative Transactions Designated And Effective As Cash Flow Hedges) (Detail) - Power [Member] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value of Cash Flow Hedges	$ 1	$ 18
Impact on Accumulated Other Comprehensive Income (Loss) (after tax)	$ 1	$ 10