Income Tax - Schedule of Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
STATUTORY TAX RATE
Federal	21.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%	4.00%
Cost of removal	1.00%	1.00%	(1.00%)
Other plant-related items	(1.00%)	(1.00%)	0.00%
TCJA deferred tax re-measurement	2.00%	(13.00%)	0.00%
Amortization of excess deferred federal income taxes	(3.00%)	(0.00%)	(0.00%)
Renewable energy credits	(1.00%)	(1.00%)	(1.00%)
Research and development credits	(0.00%)	(0.00%)	(1.00%)
Other	0.00%	(2.00%)	0.00%
Effective tax rate	23.00%	23.00%	36.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	35.00%	35.00%
Changes in computed taxes resulting from:
State income tax	5.00%	4.00%	4.00%
Cost of removal	1.00%	1.00%	(1.00%)
Other plant-related items	(1.00%)	(1.00%)	(1.00%)
TCJA deferred tax re-measurement	0.00%	0.00%	0.00%
Amortization of excess deferred federal income taxes	(3.00%)	(0.00%)	(0.00%)
Renewable energy credits	(0.00%)	(0.00%)	(0.00%)
Research and development credits	(1.00%)	(0.00%)	(1.00%)
Other	(1.00%)	(1.00%)	0.00%
Effective tax rate	21.00%	38.00%	36.00%