Consolidated Statement of Common Shareholders' Equity (USD $) In Millions, except Share data	Total	CECONY [Member]	Common Stock [Member]	Common Stock [Member] CECONY [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] CECONY [Member]	Retained Earnings [Member]	Retained Earnings [Member] CECONY [Member]	Treasury Stock [Member]	Capital Stock Expense [Member]	Capital Stock Expense [Member] CECONY [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Accumulated Other Comprehensive Income/(Loss) [Member] CECONY [Member]	Repurchased Con Edison Stock [Member] CECONY [Member]
BALANCE at Dec. 31, 2011	$ 11,436	$ 10,218	$ 32	$ 589	$ 4,991	$ 4,234	$ 7,568	$ 6,429	$ (1,033)	$ (64)	$ (64)	$ (58)	$ (8)	$ (962)
BALANCE (In Shares) at Dec. 31, 2011			292,888,521	235,488,094					23,194,075
Net income for common stock	277						277
NET INCOME		276						276
Common stock dividends	(177)	(171)					(177)	(171)
Issuance of common shares for stock plans, net of repurchases	(2)								(2)
Cumulative preferred dividends		(3)						(3)
Issuance of common shares for stock plans, net of repurchases (In Shares)			(7,225)						7,225
Preferred stock redemption	4	4								4	4
Other comprehensive income (loss)	7											7
BALANCE at Mar. 31, 2012	11,545	10,324	32	589	4,991	4,234	7,668	6,531	(1,035)	(60)	(60)	(51)	(8)	(962)
BALANCE (In Shares) at Mar. 31, 2012			292,881,296	235,488,094					23,201,300
BALANCE at Dec. 31, 2011	11,436	10,218		589	4,991	4,234								(962)
BALANCE (In Shares) at Dec. 31, 2011				235,488,094
Net income for common stock	931	824
NET INCOME	934	827
Cumulative preferred dividends	(3)	(3)
BALANCE at Sep. 30, 2012	11,842	10,532		589	4,991	4,234				(61)	(60)		(10)	(962)
BALANCE (In Shares) at Sep. 30, 2012				235,488,094
BALANCE at Mar. 31, 2012	11,545	10,324	32	589	4,991	4,234	7,668	6,531	(1,035)	(60)		(51)	(8)	(962)
BALANCE (In Shares) at Mar. 31, 2012			292,881,296	235,488,094					23,201,300
Net income for common stock	214						214
NET INCOME		163						163
Common stock dividends	(178)	(171)					(178)	(171)
Issuance of common shares for stock plans, net of repurchases	(1)									(1)
Issuance of common shares for stock plans, net of repurchases (In Shares)			1,700						(1,700)
Other comprehensive income (loss)	(1)	(2)										(1)	(2)
BALANCE at Jun. 30, 2012	11,579	10,314	32	589	4,991	4,234	7,704	6,523	(1,035)	(61)	(60)	(52)	(10)	(962)
BALANCE (In Shares) at Jun. 30, 2012			292,882,996	235,488,094					23,199,600
Net income for common stock	440	389					440
NET INCOME	440	389						389
Common stock dividends	(177)	(171)					(177)	(171)
Issuance of common shares for stock plans, net of repurchases	(2)								(2)
Issuance of common shares for stock plans, net of repurchases (In Shares)			(11,100)						11,100
Other comprehensive income (loss)	2											2
BALANCE at Sep. 30, 2012	11,842	10,532	32	589	4,991	4,234	7,967	6,741	(1,037)	(61)	(60)	(50)	(10)	(962)
BALANCE (In Shares) at Sep. 30, 2012			292,871,896	235,488,094					23,210,700
BALANCE at Dec. 31, 2012	11,869	10,552	32	589	4,991	4,234	7,997	6,761	(1,037)	(61)	(61)	(53)	(9)	(962)
BALANCE (In Shares) at Dec. 31, 2012			292,871,896	235,488,094					23,210,700
Net income for common stock	192						192
NET INCOME		277						277
Common stock dividends	(180)	(182)					(180)	(182)
Issuance of common shares for stock plans, net of repurchases	5				(2)				7
Issuance of common shares for stock plans, net of repurchases (In Shares)			95,468						(95,468)
Other comprehensive income (loss)	3											3
BALANCE at Mar. 31, 2013	11,889	10,647	32	589	4,989	4,234	8,009	6,856	(1,030)	(61)	(61)	(50)	(9)	(962)
BALANCE (In Shares) at Mar. 31, 2013			292,967,364	235,488,094					23,115,232
BALANCE at Dec. 31, 2012	11,869	10,552		589		4,234				(61)	(61)		(9)	(962)
BALANCE (In Shares) at Dec. 31, 2012				235,488,094
Net income for common stock	828	831
NET INCOME	828	831
BALANCE at Sep. 30, 2013	12,166	10,838		589	4,990	4,234				(61)	(61)		(9)	(962)
BALANCE (In Shares) at Sep. 30, 2013				235,488,094
BALANCE at Mar. 31, 2013	11,889	10,647	32	589	4,989	4,234	8,009	6,856	(1,030)	(61)	(61)	(50)	(9)	(962)
BALANCE (In Shares) at Mar. 31, 2013			292,967,364	235,488,094					23,115,232
Net income for common stock	172						172
NET INCOME		153						153
Common stock dividends	(180)	(182)					(180)	(182)
Issuance of common shares for stock plans, net of repurchases					1				(1)
Issuance of common shares for stock plans, net of repurchases (In Shares)			(4,078)						4,078
Other comprehensive income (loss)	2											2
BALANCE at Jun. 30, 2013	11,883	10,618	32	589	4,990	4,234	8,001	6,827	(1,031)	(61)	(61)	(48)	(9)	(962)
BALANCE (In Shares) at Jun. 30, 2013			292,963,286	235,488,094					23,119,310
Net income for common stock	464	401					464
NET INCOME	464	401						401
Common stock dividends	(180)	(181)					(180)	(181)
Issuance of common shares for stock plans, net of repurchases	(3)								(3)
Issuance of common shares for stock plans, net of repurchases (In Shares)			(34,931)						34,931
Other comprehensive income (loss)	2											2
BALANCE at Sep. 30, 2013	$ 12,166	$ 10,838	$ 32	$ 589	$ 4,990	$ 4,234	$ 8,285	$ 7,047	$ (1,034)	$ (61)	$ (61)	$ (46)	$ (9)	$ (962)
BALANCE (In Shares) at Sep. 30, 2013			292,928,355	235,488,094					23,154,241