Revenue Recognition - Additional information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected	$ 18
CECONY
Disaggregation of Revenue [Line Items]
Late fee and other fees not collected	$ 17
O&R | COVID-19
Disaggregation of Revenue [Line Items]
Late payment charges and fees		$ 52
Late payment charges and fees, surcharge recovery period	12 months