Consolidated Statement of Equity/Shareholder's Equity (Unaudited) - USD ($) $ in Millions	Total	CECONY	Common Stock	Common Stock CECONY	Additional Paid-In Capital	Additional Paid-In Capital CECONY	Retained Earnings	Retained Earnings CECONY	Repurchased Con Edison Stock CECONY	Treasury Stock	Capital Stock Expense	Capital Stock Expense CECONY	Accumulated Other Comprehensive Income/(Loss)	Accumulated Other Comprehensive Income/(Loss) CECONY	Noncontrolling Interest
Beginning Balance at Dec. 31, 2014	$ 12,585		$ 32		$ 4,991		$ 8,691			$ (1,032)	$ (61)		$ (45)	$ (11)	$ 9
Beginning Balance at Dec. 31, 2014		$ 11,188		$ 589		$ 4,234		$ 7,399	$ (962)			$ (61)		(11)
Beginning Balance (in shares) at Dec. 31, 2014			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	370	348					370	348
Common stock dividends	(190)	(338)					(190)	(338)
Issuance of common shares for stock plans, net of repurchases					2					$ (2)
Other comprehensive income	5	0											5	0
Ending Balance at Mar. 31, 2015		11,198		$ 589		4,234		7,409	(962)			(61)		(11)
Ending Balance at Mar. 31, 2015	12,770		$ 32		4,993		8,871			$ (1,034)	(61)		(40)		9
Ending Balance (in shares) at Mar. 31, 2015			293,000,000	235,000,000						23,000,000
Beginning Balance at Dec. 31, 2014	12,585		$ 32		4,991		8,691			$ (1,032)	(61)		(45)	(11)	9
Beginning Balance at Dec. 31, 2014		11,188		$ 589		4,234		7,399	(962)			(61)		(11)
Beginning Balance (in shares) at Dec. 31, 2014			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,017	935
Ending Balance at Sep. 30, 2015		11,430		$ 589		4,234		7,639	(962)			(61)		(9)
Ending Balance at Sep. 30, 2015	13,049		$ 32		5,008		9,137			$ (1,038)	(61)		(38)	(9)	9
Ending Balance (in shares) at Sep. 30, 2015			293,000,000	235,000,000						23,000,000
Beginning Balance at Mar. 31, 2015	12,770		$ 32		4,993		8,871			$ (1,034)	(61)		(40)		9
Beginning Balance at Mar. 31, 2015		11,198		$ 589		4,234		7,409	(962)			(61)		(11)
Beginning Balance (in shares) at Mar. 31, 2015			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	219	211					219	211
Common stock dividends	(190)	(178)					(190)	(178)
Issuance of common shares for stock plans, net of repurchases	(3)									$ (3)
Other comprehensive income	1	1											1	1
Ending Balance at Jun. 30, 2015		11,232		$ 589		4,234		7,442	(962)			(61)		(10)
Ending Balance at Jun. 30, 2015	12,797		$ 32		4,993		8,900			$ (1,037)	(61)		(39)	(10)	9
Ending Balance (in shares) at Jun. 30, 2015			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	428	375					428	375
Common stock dividends	(191)	(178)					(191)	(178)
Issuance of common shares for stock plans, net of repurchases	14				15					$ (1)
Other comprehensive income	1	1											1	1
Ending Balance at Sep. 30, 2015		11,430		$ 589		4,234		7,639	(962)			(61)		(9)
Ending Balance at Sep. 30, 2015	13,049		$ 32		5,008		9,137			$ (1,038)	(61)		(38)	(9)	9
Ending Balance (in shares) at Sep. 30, 2015			293,000,000	235,000,000						23,000,000
Beginning Balance at Dec. 31, 2015	13,061		$ 32		5,030		9,123			$ (1,038)	(61)		(34)	(9)	9
Beginning Balance at Dec. 31, 2015	13,052	11,415		$ 589		4,247		7,611	(962)			(61)		(9)
Beginning Balance (in shares) at Dec. 31, 2015			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	310	310					310	310
Common stock dividends	(197)	(186)					(197)	(186)
Issuance of common shares for stock plans, net of repurchases	28				28
Issuance of common shares for stock plans, net of repurchases (in shares)			1,000,000
Capital contribution by parent		23				23
Other comprehensive income	0	0											0	0
Noncontrolling interest	(1)														(1)
Ending Balance at Mar. 31, 2016		11,562		$ 589		4,270		7,735	(962)			(61)		(9)
Ending Balance at Mar. 31, 2016	13,201		$ 32		5,058		9,236			$ (1,038)	(61)		(34)		8
Ending Balance (in shares) at Mar. 31, 2016			294,000,000	235,000,000						23,000,000
Beginning Balance at Dec. 31, 2015	13,061		$ 32		5,030		9,123			$ (1,038)	(61)		(34)	(9)	9
Beginning Balance at Dec. 31, 2015	13,052	11,415		$ 589		4,247		7,611	(962)			(61)		(9)
Beginning Balance (in shares) at Dec. 31, 2015			293,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,039	859
Ending Balance at Sep. 30, 2016	14,267	11,793		$ 589		4,323		7,912	(962)			(61)		(8)
Ending Balance at Sep. 30, 2016	14,275		$ 33		5,830		9,557			$ (1,038)	(83)		(32)	(8)	8
Ending Balance (in shares) at Sep. 30, 2016			305,000,000	235,000,000						23,000,000
Beginning Balance at Mar. 31, 2016	13,201		$ 32		5,058		9,236			$ (1,038)	(61)		(34)		8
Beginning Balance at Mar. 31, 2016		11,562		$ 589		4,270		7,735	(962)			(61)		(9)
Beginning Balance (in shares) at Mar. 31, 2016			294,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	232	161					232	161
Common stock dividends	(204)	(186)					(204)	(186)
Issuance of common shares - public offering	702		$ 1		723						(22)
Issuance of common shares - public offering (in shares)			10,000,000
Issuance of common shares for stock plans, net of repurchases	26				26
Capital contribution by parent		28				28
Other comprehensive income	1	1											1	1
Ending Balance at Jun. 30, 2016		11,566		$ 589		4,298		7,710	(962)			(61)		(8)
Ending Balance at Jun. 30, 2016	13,958		$ 33		5,807		9,264			$ (1,038)	(83)		(33)	(8)	8
Ending Balance (in shares) at Jun. 30, 2016			304,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	497	388					497	388
Common stock dividends	(204)	(186)					(204)	(186)
Issuance of common shares for stock plans, net of repurchases	23				23
Issuance of common shares for stock plans, net of repurchases (in shares)			1,000,000
Capital contribution by parent		25				25
Other comprehensive income	1	0											1	0
Ending Balance at Sep. 30, 2016	14,267	$ 11,793		$ 589		$ 4,323		$ 7,912	$ (962)			$ (61)		(8)
Ending Balance at Sep. 30, 2016	$ 14,275		$ 33		$ 5,830		$ 9,557			$ (1,038)	$ (83)		$ (32)	$ (8)	$ 8
Ending Balance (in shares) at Sep. 30, 2016			305,000,000	235,000,000						23,000,000