Pension, OPEB and Savings Plans (Schedule Of Percentage Of Fair Value Of Total Plan Assets) (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	100.00%	100.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	66.00%	69.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	32.00%	29.00%
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	2.00%	2.00%
Long Island Electric Utility Servco LLC Pension and OPEB [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	100.00%	100.00%
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	67.00%	72.00%
Long Island Electric Utility Servco LLC Pension and OPEB [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Actual plan asset allocation, percent	33.00%	28.00%