Income Taxes - Reconciliation to Effective Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	21.10%	2.80%
Plant basis differences	(3.60%)	(3.40%)
Excess deferred tax amortization	(11.50%)	(12.00%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	1.70%	(0.30%)
Other	2.60%	(1.10%)
Effective income tax rate	31.20%	6.90%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 67
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	40
Income Tax Credits and Adjustments	15
Total transaction costs relating to the Separation	$ 19
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	8.00%	6.80%
Plant basis differences	(0.60%)	(0.60%)
Excess deferred tax amortization	(6.30%)	(6.90%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.30%)	(0.20%)
Other	0.00%	(3.50%)
Effective income tax rate	21.70%	16.50%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(0.10%)	(1.60%)
Plant basis differences	(11.30%)	(10.50%)
Excess deferred tax amortization	(3.20%)	(3.20%)
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	0.00%	0.00%
Other	0.00%	(0.10%)
Effective income tax rate	6.40%	5.60%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	2.40%	(10.10%)
Plant basis differences	(0.90%)	(1.40%)
Excess deferred tax amortization	(17.60%)	(15.50%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	(0.40%)
Other	(0.10%)	(0.10%)
Effective income tax rate	4.30%	(6.60%)
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	3.70%	6.10%
Plant basis differences	(1.60%)	(1.50%)
Excess deferred tax amortization	(17.70%)	(19.30%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	(0.20%)
Other	0.20%	(0.10%)
Effective income tax rate	5.10%	5.90%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(4.50%)	5.50%
Plant basis differences	(2.60%)	(2.10%)
Excess deferred tax amortization	(17.40%)	(15.10%)
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	(0.20%)
Other	(0.60%)	0.10%
Effective income tax rate	(4.50%)	9.20%
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.20%	6.40%
Plant basis differences	(0.70%)	(0.70%)
Excess deferred tax amortization	(19.40%)	(18.50%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.30%)	(0.10%)
Other	0.10%	0.30%
Effective income tax rate	6.70%	8.20%
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.80%	6.90%
Plant basis differences	(1.30%)	(0.90%)
Excess deferred tax amortization	(22.20%)	(28.70%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.30%)	(0.30%)
Other	(0.10%)	2.20%
Effective income tax rate	3.70%	0.00%