Income Tax - Schedule of Differences on Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities:
Property basis differences	$ 8,298	$ 7,985
Regulatory assets:
Unrecognized pension and other postretirement costs	36	910
Environmental remediation costs	264	243
Deferred storm costs	33	31
Other regulatory assets	640	536
Operating lease right-of-use asset	204	220
Pension Asset Reserve	478	0
Equity investments	0	46
Other	30	0
Total deferred tax liabilities	9,983	9,971
Deferred tax assets:
Accrued pension and other postretirement costs	218	504
Future income tax	554	617
Other regulatory liabilities	727	656
Superfund and other environmental costs	264	241
Asset retirement obligations	177	178
Operating lease liabilities	195	211
Loss carryforwards	144	164
Tax credits carryforward	946	1,022
Valuation allowance	(22)	(22)
Equity investments	34	0
Other	0	59
Total deferred tax assets	3,237	3,630
Net deferred tax liabilities	6,746	6,341
Unamortized investment tax credits	127	134
Net deferred tax liabilities and unamortized investment tax credits	6,873	6,475
CECONY
Deferred tax liabilities:
Property basis differences	7,213	6,901
Regulatory assets:
Unrecognized pension and other postretirement costs	31	861
Environmental remediation costs	241	222
Deferred storm costs	0	0
Other regulatory assets	609	508
Operating lease right-of-use asset	155	165
Pension Asset Reserve	471	0
Equity investments	0	0
Other	0	0
Total deferred tax liabilities	8,720	8,657
Deferred tax assets:
Accrued pension and other postretirement costs	188	427
Future income tax	517	579
Other regulatory liabilities	620	570
Superfund and other environmental costs	238	219
Asset retirement obligations	141	143
Operating lease liabilities	155	165
Loss carryforwards	38	34
Tax credits carryforward	0	0
Valuation allowance	0	0
Equity investments	0	0
Other	42	127
Total deferred tax assets	1,939	2,264
Net deferred tax liabilities	6,781	6,393
Unamortized investment tax credits	15	18
Net deferred tax liabilities and unamortized investment tax credits	$ 6,796	$ 6,411