Schedule I - Condensed Financial Information - Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	$ 1,343	$ 1,382	$ 1,525
Change in Assets:
Taxes receivable	29	27	15
Other – net	54	(62)	0
NET CASH FLOWS FROM OPERATING ACTIVITIES	3,134	2,695	3,367
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,782)	(5,471)	(3,710)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(874)	1,989	(477)
Issuance of long-term debt	3,017	3,030	1,697
Retirement of long-term debt	(1,195)	(1,938)	(434)
Debt issuance costs	(32)	(61)	(19)
Issuance of common shares for stock plans	54	53	51
Issuance of common shares - public offering	825	705	343
Common stock dividends	(924)	(842)	(803)
NET CASH FLOWS FROM FINANCING ACTIVITIES	859	2,938	357
NET CHANGE FOR THE PERIOD	211	162	14
BALANCE AT BEGINNING OF PERIOD	1,006	844	830
BALANCE AT END OF PERIOD	1,217	1,006	844
CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,250	1,196	1,104
Change in Assets:
Other – net	54	(96)	23
NET CASH FLOWS FROM OPERATING ACTIVITIES	2,502	2,204	2,866
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,124)	(3,306)	(3,080)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(55)	1,042	(450)
Issuance of long-term debt	1,300	2,740	1,200
Retirement of long-term debt	(475)	(1,836)	0
Debt issuance costs	(21)	(30)	(15)
NET CASH FLOWS FROM FINANCING ACTIVITIES	737	1,190	240
NET CHANGE FOR THE PERIOD	115	88	26
BALANCE AT BEGINNING OF PERIOD	818	730	704
BALANCE AT END OF PERIOD	933	818	730
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,343	1,382	1,525
Equity in earnings of subsidiaries	(1,354)	(1,447)	(1,544)
Change in Assets:
Special deposits	(3)	(8)	0
Taxes receivable	25	2	34
Other – net	44	187	21
NET CASH FLOWS FROM OPERATING ACTIVITIES	1,029	1,033	896
INVESTING ACTIVITIES
Contributions to subsidiaries	(930)	(1,110)	(434)
Debt receivable from affiliated companies	450	(825)	0
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(480)	(1,935)	(434)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(783)	164	(53)
Issuance of long-term debt	825	825	400
Retirement of long-term debt	(553)	(3)	(402)
Debt issuance costs	0	0	(2)
Issuance of common shares for stock plans	54	53	51
Issuance of common shares - public offering	825	705	343
Common stock dividends	(924)	(842)	(803)
NET CASH FLOWS FROM FINANCING ACTIVITIES	(556)	902	(466)
NET CHANGE FOR THE PERIOD	(7)	0	(4)
BALANCE AT BEGINNING OF PERIOD	9	9	13
BALANCE AT END OF PERIOD	2	9	9
Parent Company | CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	912	846	796
Parent Company | O&R
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	47	46	44
Parent Company | Clean Energy Businesses
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	3	15	12
Parent Company | Con Edison Transmission
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	$ 12	$ 10	$ 8