Consolidated Statement of Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Capital Stock Expense	Accumulated Other Comprehensive Income/(Loss)	Noncontrolling Interest	CECONY	CECONY Common Stock	CECONY Additional Paid-In Capital	CECONY Retained Earnings	CECONY Repurchased Con Edison Stock	CECONY Capital Stock Expense	CECONY Accumulated Other Comprehensive Income/(Loss)
BALANCE AS OF BEGINNING OF PERIOD (in shares) at Dec. 31, 2014		293,000,000								235,000,000
BALANCE AS OF BEGINNING OF PERIOD at Dec. 31, 2014	$ 12,585	$ 32	$ 4,991	$ 8,691	$ (1,032)	$ (61)	$ (45)	$ 9							$ (11)
BALANCE AS OF BEGINNING OF PERIOD at Dec. 31, 2014									$ 11,188	$ 589	$ 4,234	$ 7,399	$ (962)	$ (61)	(11)
TREASURY STOCK, BALANCE AS OF BEGINNING OF PERIOD (in shares) at Dec. 31, 2014					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,193			1,193					1,084			1,084
Common stock dividends	(761)			(761)					(872)			(872)
Issuance of common shares for stock plans, net of repurchases (in shares)		0			0
Issuance of common shares for stock plans, net of repurchases	33		39		$ (6)
Capital contribution by parent									13		13
Other comprehensive income	11						11		2						2
Noncontrolling interest	0
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2015		293,000,000								235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2015	13,061	$ 32	5,030	9,123	$ (1,038)	(61)	(34)	9							(9)
BALANCE AS OF END OF PERIOD at Dec. 31, 2015									11,415	$ 589	4,247	7,611	(962)	(61)	(9)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2015					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,245			1,245					1,056			1,056
Common stock dividends	(809)			(809)					(744)			(744)
Issuance of common shares - public offering (in shares)		10,000,000
Issuance of common shares - public offering	702	$ 1	723			(22)
Issuance of common shares for stock plans (in shares)		2,000,000
Issuance of common shares for stock plans	101		101
Capital contribution by parent									100		100
Other comprehensive income	7						7		2						2
Noncontrolling interest	(1)							(1)
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2016		305,000,000								235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2016	14,306	$ 33	5,854	9,559	$ (1,038)	(83)	(27)	8							(7)
BALANCE AS OF END OF PERIOD at Dec. 31, 2016	14,298								11,829	$ 589	4,347	7,923	(962)	(61)	(7)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2016					23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,525			1,525					1,104			1,104
Common stock dividends	(849)			(849)					(796)			(796)
Issuance of common shares - public offering (in shares)		5,000,000
Issuance of common shares - public offering	343	$ 1	344			(2)
Issuance of common shares for stock plans	100		100
Capital contribution by parent									301		302			(1)
Other comprehensive income	1						1		$ 1						1
Noncontrolling interest	(1)							(1)
BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2017		310,000,000							21,976,200	235,000,000
BALANCE AS OF END OF PERIOD at Dec. 31, 2017	15,425	$ 34	$ 6,298	$ 10,235	$ (1,038)	$ (85)	$ (26)	$ 7							(6)
BALANCE AS OF END OF PERIOD at Dec. 31, 2017	$ 15,418								$ 12,439	$ 589	$ 4,649	$ 8,231	$ (962)	$ (62)	$ (6)
TREASURY STOCK, BALANCE AS OF END OF PERIOD (in shares) at Dec. 31, 2017					23,000,000