Income Tax - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	$ 17.0	$ 14.0	$ 13.0	$ 6.0
Effective income tax rate reconciliation, uncertainty of taxes	12.0
Unrecognized tax benefits that would have an impact on effective tax rate	17.0
Unrecognized tax benefits that would have an impact on effective tax rate, net of tax	16.0
General Business Tax Credit
Operating Loss Carryforwards [Line Items]
Tax credit carryovers	946.0
Tax Year 2018 Through 2013
Operating Loss Carryforwards [Line Items]
Operating loss carryback	29.0
Net tax refund		2.5
Tax Year 2013
Operating Loss Carryforwards [Line Items]
Discrete income tax benefit		4.0
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	21.5
State | New York State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,130.0
State | New York City
Operating Loss Carryforwards [Line Items]
Valuation allowance reversed	5.0
Deferred tax assets	17.0
CECONY
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	5.0	$ 3.0	$ 2.0	$ 4.0
Effective income tax rate reconciliation, uncertainty of taxes	3.0
Unrecognized tax benefits that would have an impact on effective tax rate	$ 5.0