Consolidated Statement of Equity/Shareholder's Equity (Unaudited) - USD ($) shares in Millions, $ 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)
Beginning Balance at Dec. 31, 2016							$ (27)								$ (7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 563								$ 482
Other comprehensive income	0								0
Ending Balance at Jun. 30, 2017							(27)								(7)
Beginning Balance at Mar. 31, 2017							(28)								(7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	175								143
Other comprehensive income	1								0
Ending Balance at Jun. 30, 2017							(27)								(7)
Beginning Balance (in shares) at Dec. 31, 2017		310			23					235
Beginning Balance at Dec. 31, 2017	15,425	$ 34	$ 6,298	$ 10,235	$ (1,038)	$ (85)	(26)	$ 7							(6)
Beginning Balance at Dec. 31, 2017	15,418								12,439	$ 589	$ 4,649	$ 8,231	$ (962)	$ (62)	(6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	616			616					538			538
Common stock dividends	(444)			(444)					(423)			(423)
Issuance of common shares for stock plans (in shares)		1
Issuance of common shares for stock plans	52		52
Capital contribution by parent									70		70
Other comprehensive income	6						6		1						1
Ending Balance (in shares) at Jun. 30, 2018		311			23					235
Ending Balance at Jun. 30, 2018	15,655	$ 34	6,350	10,407	$ (1,038)	(85)	(20)	7							(5)
Ending Balance at Jun. 30, 2018	15,648								12,625	$ 589	4,719	8,346	(962)	(62)	(5)
Beginning Balance at Mar. 31, 2018							(22)								(6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	188								149
Other comprehensive income	2								1
Ending Balance (in shares) at Jun. 30, 2018		311			23					235
Ending Balance at Jun. 30, 2018	15,655	$ 34	$ 6,350	$ 10,407	$ (1,038)	$ (85)	$ (20)	$ 7							(5)
Ending Balance at Jun. 30, 2018	$ 15,648								$ 12,625	$ 589	$ 4,719	$ 8,346	$ (962)	$ (62)	$ (5)