Schedule I - Condensed Financial Information - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	$ 1,525	$ 1,245	$ 1,193
Change in Assets:
Taxes receivable	15	87	58
Other – net	(44)	54	(27)
NET CASH FLOWS FROM OPERATING ACTIVITIES	3,367	3,459	3,277
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,703)	(4,976)	(3,657)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(477)	(475)	729
Issuance of long-term debt	1,697	2,590	1,147
Retirement of long-term debt	(434)	(735)	(500)
Debt issuance costs	(19)	(24)	(15)
Issuance of common shares for stock plans, net of repurchases	51	51	1
Issuance of common shares - public offering	343	702	0
Common stock dividends	(803)	(763)	(733)
NET CASH FLOWS FROM FINANCING ACTIVITIES	357	1,345	629
NET CHANGE FOR THE PERIOD	21	(172)	249
BALANCE AT BEGINNING OF PERIOD	776	944	699
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	797	776	944
CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,104	1,056	1,084
Change in Assets:
Other – net	8	(11)	38
NET CASH FLOWS FROM OPERATING ACTIVITIES	2,866	3,038	2,819
INVESTING ACTIVITIES
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(3,078)	(2,739)	(2,638)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(450)	(433)	583
Issuance of long-term debt	1,200	1,300	650
Retirement of long-term debt	0	(650)	(350)
Debt issuance costs	(15)	(13)	(7)
NET CASH FLOWS FROM FINANCING ACTIVITIES	240	(440)	17
NET CHANGE FOR THE PERIOD	28	(141)	198
BALANCE AT BEGINNING OF PERIOD	702	843	645
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	730	702	843
Parent Company
Condensed Cash Flow Statements, Captions [Line Items]
Net Income	1,525	1,245	1,193
Equity in earnings of subsidiaries	(1,544)	(1,254)	(1,195)
Change in Assets:
Special deposits	0	0	0
Taxes receivable	34	87	58
Other – net	21	(152)	(382)
NET CASH FLOWS FROM OPERATING ACTIVITIES	896	723	635
INVESTING ACTIVITIES
Contributions to subsidiaries	(434)	(691)	(15)
Long term debt receivable from affiliated companies	0	(900)	0
NET CASH FLOWS USED IN INVESTING ACTIVITIES	(434)	(1,591)	(15)
FINANCING ACTIVITIES
Net proceeds of short-term debt	(53)	(53)	162
Issuance of long-term debt	400	900	0
Retirement of long-term debt	(402)	(2)	(2)
Debt issuance costs	(2)	(5)	0
Issuance of common shares for stock plans, net of repurchases	51	51	1
Issuance of common shares - public offering	343	702	0
Common stock dividends	(803)	(763)	(733)
NET CASH FLOWS FROM FINANCING ACTIVITIES	(466)	830	(572)
NET CHANGE FOR THE PERIOD	(4)	(38)	48
BALANCE AT BEGINNING OF PERIOD	13	51	3
BALANCE AT END OF PERIOD EXCLUDING HELD FOR SALE	9	13	51
Parent Company | CECONY
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	796	744	872
Parent Company | O&R
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	44	43	81
Parent Company | Clean Energy Businesses
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	12	10	8
Parent Company | Con Edison Transmission
Condensed Cash Flow Statements, Captions [Line Items]
Dividends received	$ 8	$ 0	$ 0