Available-For-Sale Securities (Fair Value Of Rabbi Trust) (Detail) - Rabbi Trust [Member] - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total Rabbi Trust Available-for-Sale Securities	$ 212	$ 191
Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Rabbi Trust Available-for-Sale Securities	52	45
PSE And G [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Rabbi Trust Available-for-Sale Securities	42	41
Other Entity [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Rabbi Trust Available-for-Sale Securities	$ 118	$ 105