Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 20,623	$ 20,336	$ 19,282	$ 19,065	$ 20,336	$ 19,065
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5		2	4	5	6
Ending balance	20,621	20,623	20,053	19,282	20,621	20,053
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		20,037			20,037
Ending Balance	20,387				20,387
Subsidiaries
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES		1
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	16,618	16,312	15,192	14,849	16,312	14,849
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0		0		1	0
Ending Balance	16,568	16,618	15,924	15,192	16,568	15,924
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	5	5	(21)	(25)	5	(25)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5		2	4
Ending balance	10	5	(19)	(21)	10	(19)
AOCI Attributable to Parent | Subsidiaries
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES		1
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1	0	(7)	(7)	0	(7)
Ending Balance	1	$ 1	(7)	$ (7)	1	(7)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	5		0		4	2
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	0		2		1	4
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	5		2		5	6
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, tax	(1)				(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax			(1)		(1)	(1)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	0		0		(1)	0
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0		0		1	0
CECONY | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Ending Balance	16,568				16,568
CECONY | Accumulated Defined Benefit Plans Adjustment Attributable to Parent | Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	$ 0		$ 0		$ 0	$ 0