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, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 18,467	$ 18,213	$ 17,501	$ 16,839	$ 18,213	$ 16,839
Beginning Balance		18,022			18,022
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	5	1	4	5	5
Ending Balance	18,441	18,467	17,865	17,501	18,441	17,865
Ending Balance	18,225				18,225
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(14)	(19)	(12)	(16)	(19)	(16)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES		5	1	4
Ending Balance	(14)	(14)	(11)	(12)	(14)	(11)
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	0		1		1	3
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0		1		5	5
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	14,333	14,147	13,319	12,910	14,147	12,910
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	1	0	0	2	0
Ending Balance	14,265	14,333	13,868	13,319	14,265	13,868
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5)	(6)	(5)	(5)	(6)	(5)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	1
Ending Balance	(4)	$ (5)	(5)	$ (5)	(4)	(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		2	0
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	$ 1		$ 0		2	0
OCI before reclassifications, tax					(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax					$ (1)	$ (1)