Revenue Recognition - Additional information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected		$ 12	$ 18	$ 49	$ 38
CECONY | Subsidiaries
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected		$ 11	$ 17	$ 46	$ 36
O&R | COVID-19 | Subsidiaries
Disaggregation of Revenue [Line Items]
Late payment charges and fees	$ 52
Late payment charges and fees, surcharge recovery period				12 months