Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 16,839	$ 15,425
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	4
Ending Balance	17,501	15,661
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(16)	(26)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	4
Ending Balance	(12)	(22)
Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax of $(1) for Con Edison in 2019 and 2018	2	3
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(1) for Con Edison in 2018	2	1
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	4
OCI before reclassifications, tax	(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax		(1)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	0
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5)	(6)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES
Ending Balance	(5)	(6)
CECONY | Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax of $(1) for Con Edison in 2019 and 2018	0	0
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(1) for Con Edison in 2018	0	0
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	$ 0	$ 0