Schedule I - Condensed Financial Information - Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	$ 1,101	$ 1,343	$ 1,382	$ 1,525
Change in Assets:
Taxes receivable	(6)	29	27
Other – net	(134)	54	(62)
NET CASH FLOWS FROM OPERATING ACTIVITIES	2,198	3,134	2,695
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(4,224)	(3,782)	(5,471)
FINANCING ACTIVITIES
Net proceeds of short-term debt	178	(874)	1,989
Issuance of long-term debt	2,925	3,017	3,030
Retirement of long-term debt	(518)	(1,195)	(1,938)
Debt issuance costs	(47)	(32)	(61)
Issuance of common shares for stock plans	58	54	53
Issuance of common shares - public offering	640	825	705
Common stock dividends	(975)	(924)	(842)
NET CASH FLOWS FROM FINANCING ACTIVITIES	2,245	859	2,938
NET CHANGE FOR THE PERIOD	219	211	162
BALANCE AT BEGINNING OF PERIOD	1,217	1,006	844
BALANCE AT END OF PERIOD	1,436	1,217	1,006	844
CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,185	1,250	1,196
Change in Assets:
Other – net	(49)	54	(96)
NET CASH FLOWS FROM OPERATING ACTIVITIES	1,693	2,502	2,204
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,416)	(3,124)	(3,306)
FINANCING ACTIVITIES
Net proceeds of short-term debt	523	(55)	1,042
Issuance of long-term debt	2,200	1,300	2,740
Retirement of long-term debt	(350)	(475)	(1,836)
Debt issuance costs	(34)	(21)	(30)
NET CASH FLOWS FROM FINANCING ACTIVITIES	1,857	737	1,190
NET CHANGE FOR THE PERIOD	134	115	88
BALANCE AT BEGINNING OF PERIOD	933	818	730
BALANCE AT END OF PERIOD	1,067	933	818	730
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,101	1,343	1,382
Equity in earnings of subsidiaries	(1,105)	(1,354)	(1,447)
Change in Assets:
Special deposits	0	(3)	(8)
Taxes receivable		25	2
Other – net	654	44	187
NET CASH FLOWS FROM OPERATING ACTIVITIES	1,713	1,029	1,033
INVESTING ACTIVITIES
Contributions to subsidiaries	(626)	(930)	(1,110)
Debt receivable from affiliated companies	400	450	(825)
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(226)	(480)	(1,935)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(537)	(783)	164
Issuance of long-term debt	650	825	825
Retirement of long-term debt	(1,178)	(553)	(3)
Debt issuance costs	(3)	0	0
Issuance of common shares for stock plans	58	54	53
Issuance of common shares - public offering	640	825	705
Common stock dividends	(975)	(924)	(842)
NET CASH FLOWS FROM FINANCING ACTIVITIES	(1,345)	(556)	902
NET CHANGE FOR THE PERIOD	142	(7)	0
BALANCE AT BEGINNING OF PERIOD	2	9	9
BALANCE AT END OF PERIOD	144	2	9	$ 9
Parent Company | CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	982	912	846
Parent Company | O&R
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	49	47	46
Parent Company | Clean Energy Businesses
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	21	3	15
Parent Company | Con Edison Transmission
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	$ 11	$ 12	$ 10