Summary of Significant Accounting Policies and Other Matters - Changes in Accumulated Other Comprehensive Income/(Loss) by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	$ 19,065	$ 18,213	$ 16,839
BALANCE AS OF BEGINNING OF PERIOD	18,847
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	30	(6)	(3)
BALANCE AS OF END OF PERIOD	20,037	18,847
BALANCE AS OF END OF PERIOD	20,336	19,065	18,213
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	(25)	(19)	(16)
BALANCE AS OF END OF PERIOD	5	(25)	(19)
Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	22	(11)	(10)
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	8	5	7
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	30	(6)	(3)
OCI before reclassifications, tax	(8)	4	(6)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	(3)	(2)	(2)
Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	(25)	(19)	(16)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	30	(6)	(3)
BALANCE AS OF END OF PERIOD	5	(25)	(19)
CECONY
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	14,849	14,147	12,910
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	7	(1)	(1)
BALANCE AS OF END OF PERIOD	16,312	14,849	14,147
CECONY | Accumulated OCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
BALANCE AS OF BEGINNING OF PERIOD	(7)	(6)	(5)
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	7	(1)	(1)
BALANCE AS OF END OF PERIOD	0	(7)	(6)
CECONY | Pension Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
OCI before reclassifications, net of tax	5	(3)	(3)
Amounts reclassified from accumulated OCI related to pension plan liabilities, net of tax	2	2	2
TOTAL OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAXES	7	(1)	(1)
OCI before reclassifications, tax	(2)	$ 1	$ (1)
Amounts reclassified from accumulated OCI related to pension plan liabilities, tax	$ (1)