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, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.41%	3.73%	4.29%
Expected Return on Plan Assets	7.80%	7.80%	8.00%
Rate of Compensation Increase	3.90%	3.90%	3.61%
Service Cost Interest Rate	3.88%	4.53%	4.81%
Interest Cost Interest Rate	3.35%	3.63%	3.75%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.90%	3.61%	3.61%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.73%	4.29%	4.54%
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.31%	3.76%	4.37%
Expected Return on Plan Assets	7.80%	7.80%	8.00%
Rate of Compensation Increase	3.90%	3.90%	3.61%
Service Cost Interest Rate	3.90%	4.64%	4.87%
Interest Cost Interest Rate	3.39%	3.69%	3.76%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.90%	3.61%	3.61%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.76%	4.37%	4.58%
Immediate Rate	7.28%	7.93%	7.55%
Ultimate Rate	4.75%	4.75%	4.75%
Year Ultimate Rate Reached	2026	2026	2025
Total of Service Cost and Interest Cost effect of 1 percent increase	$ 1	$ 13	$ 11
Postretirement Benefit Obligation effect of 1 percent increase	21	240	191
Total of Service Cost and Interest Cost effect of 1 percent decrease	(1)	(10)	(9)
Postretirement Benefit Obligation effect of 1 percent decrease	$ (20)	$ (198)	$ (160)
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.60%	3.90%	4.61%
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	4.67%	3.96%	4.71%
Rate of Compensation Increase	3.25%	3.25%	3.25%
Immediate Rate	8.03%	7.69%	7.55%
Ultimate Rate	4.75%	4.75%	4.75%
Year Ultimate Rate Reached	2026	2026	2025
Postretirement Benefit Obligation effect of 1 percent increase	$ 108	$ 131	$ 97
Postretirement Benefit Obligation effect of 1 percent decrease	$ (83)	$ (99)	$ (75)