Trust Investments (Fair Value Of Rabbi Trust) (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	$ 233	$ 224
Power [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	59	56
PSE And G [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	46	45
Rabbi Trust [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	233	224
Rabbi Trust [Member] | Power [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	59	56
Rabbi Trust [Member] | PSE And G [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	46	45
Rabbi Trust [Member] | Other Entity [Member]
Schedule of Trust Investments [Line Items]
Total Rabbi Trust Investments	$ 128	$ 123