Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 18,213	$ 16,839
Beginning Balance	18,022
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5	4
Ending Balance	18,467	17,501
Ending Balance	18,261
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(19)	(16)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5	4
Ending Balance	(14)	(12)
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	4	2
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(1) for Con Edison in 2018	1	2
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5	4
OCI before reclassifications, tax	(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	(1)	(1)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	14,147	12,910
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	0
Ending Balance	14,333	13,319
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(6)	(5)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1
Ending Balance	(5)	(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 $(1) for Con Edison in 2018	1	0
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	0
OCI before reclassifications, tax	(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	$ (1)	$ (1)