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, 2015	$ 13,061		$ 32		$ 5,030		$ 9,123			$ (1,038)	$ (61)		$ (34)	$ (9)	$ 9
Beginning Balance at Dec. 31, 2015		$ 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	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 (loss)	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)	(9)	8
Ending Balance (in shares) at Mar. 31, 2016			294,000,000	235,000,000						23,000,000
Beginning Balance at Dec. 31, 2016	14,306		$ 33		5,854		9,559			$ (1,038)	(83)		(27)	(7)	8
Beginning Balance at Dec. 31, 2016	14,298	11,829		$ 589		4,347		7,923	(962)			(61)		(7)
Beginning Balance (in shares) at Dec. 31, 2016			305,000,000	235,000,000						23,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	388	339					388	339
Common stock dividends	(211)	(199)					(211)	(199)
Issuance of common shares for stock plans	24				24
Capital contribution by parent		22				22
Other comprehensive income (loss)	(1)	0											(1)	0
Ending Balance at Mar. 31, 2017	14,498	$ 11,991		$ 589		$ 4,369		$ 8,063	$ (962)			$ (61)		(7)
Ending Balance at Mar. 31, 2017	$ 14,506		$ 33		$ 5,878		$ 9,736			$ (1,038)	$ (83)		$ (28)	$ (7)	$ 8
Ending Balance (in shares) at Mar. 31, 2017			305,000,000	235,000,000						23,000,000