Revenue Recognition - Additional information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected		$ 19	$ 18	$ 37	$ 19
CECONY | Subsidiaries
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected		$ 18	$ 17	$ 35	$ 18
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