Pension, OPEB and Savings Plans (Assumptions Used To Determine The Benefit Obligations And Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 01, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.30%	4.41%	3.73%	3.65%
Expected Return on Plan Assets	7.80%	7.80%	7.80%
Rate of Compensation Increase	3.90%	3.90%	3.90%
Service Cost Interest Rate	4.58%	3.88%	4.53%
Interest Cost Interest Rate	4.03%	3.35%	3.63%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.90%	3.90%	3.61%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.41%	3.73%	4.29%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.20%	4.31%	3.76%
Expected Return on Plan Assets	7.79%	7.80%	7.80%
Rate of Compensation Increase	3.90%	3.90%	3.90%
Service Cost Interest Rate	4.48%	3.90%	4.64%
Interest Cost Interest Rate	3.91%	3.39%	3.69%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.90%	3.90%	3.61%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.31%	3.76%	4.37%
Immediate Rate	6.68%	7.28%	7.93%
Ultimate Rate	4.75%	4.75%	4.75%
Total of Service Cost and Interest Cost effect of 1 percent increase	$ 1	$ 1	$ 13
Postretirement Benefit Obligation effect of 1 percent increase	20	21	240
Total of Service Cost and Interest Cost effect of 1 percent decrease	(1)	(1)	(10)
Postretirement Benefit Obligation effect of 1 percent decrease	$ (18)	$ (20)	$ (198)
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.52%	4.60%	3.90%
Expected Return on Plan Assets	7.60%
Rate of Compensation Increase	3.25%	3.25%	3.25%
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.60%	4.67%	3.96%
Rate of Compensation Increase	3.25%	3.25%	3.25%
Immediate Rate	6.94%	8.03%	7.69%
Ultimate Rate	4.75%	4.75%	4.75%
Postretirement Benefit Obligation effect of 1 percent increase	$ 135	$ 108	$ 131
Postretirement Benefit Obligation effect of 1 percent decrease	$ (104)	$ (83)	$ (99)