Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 20,336	$ 19,065
Beginning Balance	20,037
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	4
Ending Balance	20,623	19,282
Ending Balance	20,378
Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	16,312	14,849
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1
Ending Balance	16,618	15,192
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	5	(25)
Ending Balance	5	(21)
Pension Plan LIabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	(1)	2
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	1	2
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	4
OCI before reclassifications, tax	1	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax		(1)
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	5	(25)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES		4
Ending Balance	5	(21)
Accumulated OCI | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	0	(7)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1
Ending Balance	1	(7)
Pension Plan Liabilities | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	1	0
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	0
CECONY | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Ending Balance	16,618
CECONY | Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	$ 0	$ 0