Capitalization - Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2018	Dec. 31, 2015
Schedule of Capitalization [Line Items]
Value of shares issued		$ 705	$ 343	$ 702
Common Stock
Schedule of Capitalization [Line Items]
Common stock, shares outstanding (in shares)	321,000,000	321,000,000	310,000,000	305,000,000		293,000,000
Shares issued (in shares)		11,000,000	5,000,000	10,000,000
Value of shares issued			$ 1	$ 1
Forward Contract
Schedule of Capitalization [Line Items]
Common stock, shares subject to forward sale agreements (in shares)	5,649,369	5,649,369			14,973,492
Share price (in dollars per share)					$ 75.537
Forward Contract | Common Stock
Schedule of Capitalization [Line Items]
Shares issued (in shares)	9,324,123
Value of shares issued	$ 705
CECONY
Schedule of Capitalization [Line Items]
Common stock, shares outstanding (in shares)	21,976,200	21,976,200
CECONY | Common Stock
Schedule of Capitalization [Line Items]
Common stock, shares outstanding (in shares)	235,000,000	235,000,000	235,000,000	235,000,000		235,000,000