Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 19,065	$ 18,213
Beginning Balance	18,847
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	5
Ending Balance	19,282	18,467
Ending Balance	19,033
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(25)	(19)
Ending Balance	(21)	(14)
Pension Plan LIabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax of $(1) for Con Edison in 2020 and 2019	2	4
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of for Con Edison	2	1
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	5
OCI before reclassifications, tax		(1)
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(25)	(19)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	4	5
Ending Balance	(21)	(14)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	14,849	14,147
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	1
Ending Balance	15,192	14,333
CECONY | Pension Plan LIabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax		(1)
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(7)	(6)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES		1
Ending Balance	(7)	(5)
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 2020 and 2019	0	0
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of for Con Edison	0	1
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	$ 0	$ 1