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, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 17,501	$ 16,839	$ 15,661	$ 15,425	$ 16,839	$ 15,425
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	4	2	4	5	6
Ending Balance	17,865	17,501	15,655	15,661	17,865	15,655
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(12)	(16)	(22)	(26)	(16)	(26)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1	4	2	4
Ending Balance	(11)	(12)	(20)	(22)	(11)	(20)
Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax of $(1) for Con Edison in 2019 and 2018					2	3
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(1) for Con Edison in 2018	1		2		3	3
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	1		2		5	6
OCI before reclassifications, tax					(1)	(1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax			(1)		(1)	(1)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	0	0	1	0	0	1
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5)	(5)	(6)	(6)	(5)	(6)
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES			1
Ending Balance	(5)	$ (5)	(5)	$ (6)	(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 2019 and 2018					0	0
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax of $(1) for Con Edison in 2018	0		1		0	1
TOTAL OTHER COMPREHENSIVE INCOME, NET OF TAXES	$ 0		$ 1		$ 0	$ 1