Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	3.80%		2.70%		2.50%	3.10%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(4.00%)		(5.40%)		(4.80%)	(0.90%)
Domestic production activities deduction	(0.00%)		(4.90%)		(0.00%)	(2.80%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%		0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.90%)		(2.30%)		(1.30%)	(1.20%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(3.00%)		(1.40%)		(4.50%)	1.20%
Production tax credits and other credits	(0.60%)				(6.20%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(2.90%)		(3.80%)		(4.10%)	(2.20%)
Noncontrolling interests	0.20%		1.70%		0.50%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.10%)		(6.40%)		(0.50%)	(1.60%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	4.30%				2.30%
Other(c)	0.80%		(1.20%)		(1.80%)	(0.90%)
Effective income tax rate	39.00%		16.40%		39.10%	29.10%
Predecessor [Member]
Increase (decrease) due to:
Domestic production activities deduction			(0.00%)
Noncontrolling interests			0.00%
Successor [Member]
Increase (decrease) due to:
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent		0.00%		0.00%
Exelon Generation Co L L C [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.60%		2.10%		2.60%	2.80%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(7.80%)		(12.50%)		(8.80%)	(1.60%)
Domestic production activities deduction	(0.00%)		(11.60%)		(0.00%)	(4.90%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%		0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(1.60%)		(5.20%)		(2.00%)	(1.90%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Production tax credits and other credits	(0.00%)				(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(5.70%)		(9.00%)		(7.60%)	(3.80%)
Noncontrolling interests	0.50%		3.90%		0.90%	0.10%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.30%)		(15.20%)		1.70%	(2.90%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	0.50%		(0.40%)		2.10%	(0.60%)
Effective income tax rate	38.40%		(12.10%)		33.90%	23.40%
Commonwealth Edison Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	7.30%		5.00%		5.40%	5.20%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%		0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.60%)		(0.30%)		(0.30%)	(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	1.90%		0.10%		0.60%	0.10%
Production tax credits and other credits	(0.00%)				(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.10%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	27.20%				5.60%
Other(c)	(0.10%)		(0.30%)		(0.00%)	(0.20%)
Effective income tax rate	67.00%				45.10%	40.00%
PECO Energy Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.40%		1.20%		1.30%	1.20%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%		0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)		(0.10%)		(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	6.70%		7.00%		8.80%	7.30%
Production tax credits and other credits	(0.00%)				(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	(0.10%)		(0.00%)		1.50%	(0.20%)
Effective income tax rate	30.70%				25.90%	29.00%
Baltimore Gas and Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	5.20%		5.30%		4.80%	5.30%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.20%		0.00%	0.20%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)		(0.20%)		(0.20%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	0.50%		0.60%		3.30%	0.40%
Production tax credits and other credits	(0.00%)				(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%		0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	0.40%		0.40%		(0.00%)	0.10%
Effective income tax rate	39.10%				36.30%	39.90%
Pepco Holdings LLC [Member]
Increase (decrease) due to:
Domestic production activities deduction						(0.00%)
Pepco Holdings LLC [Member] | Predecessor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate			35.00%			35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent			6.20%			7.10%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent			(0.00%)			(0.00%)
Domestic production activities deduction						(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent			0.00%			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference			(0.20%)			(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent			3.70%			5.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent			(1.20%)			(1.90%)
Noncontrolling interests						0.00%
Other(c)			1.10%			0.10%
Effective income tax rate			35.00%			34.80%
Pepco Holdings LLC [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	5.60%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)				(0.00%)
Domestic production activities deduction	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	5.00%
Production tax credits and other credits	(5.70%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)
Noncontrolling interests	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	0.70%
Effective income tax rate	29.10%
Delmarva Power and Light Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	5.20%		7.40%		310.50%	6.10%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)		(0.60%)		(17.90%)	(0.40%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	1.30%		3.50%		98.60%	2.00%
Production tax credits and other credits	(8.60%)				(635.90%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%			0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	(0.10%)		0.80%		(35.10%)	0.50%
Effective income tax rate	30.20%		37.50%		900.00%	38.20%
Potomac Electric Power Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	5.60%		4.80%		23.00%	4.60%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.00%)		(0.10%)		(0.20%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	6.70%		3.50%		29.00%	6.20%
Production tax credits and other credits	(2.30%)				(36.70%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%			0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	0.90%		1.40%		2.50%	0.70%
Effective income tax rate	30.70%		34.80%		63.00%	32.60%
Atlantic City Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%		35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	6.10%		5.40%		5.50%	5.50%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	0.00%		0.00%			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)		(0.30%)		(0.50%)	(0.50%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	4.60%		3.10%		(7.80%)	2.50%
Production tax credits and other credits	(2.90%)				(35.40%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.00%)		(0.00%)		(0.00%)	(0.00%)
Noncontrolling interests	0.00%		0.00%			0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	0.00%				0.00%
Other(c)	0.60%		(1.90%)		(0.40%)	(0.80%)
Effective income tax rate	32.90%		38.90%		13.80%	38.30%
Atlantic City Electric Company [Member] | Predecessor [Member]
Increase (decrease) due to:
Production tax credits and other credits		(11.10%)
Atlantic City Electric Company [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		11.90%		4.40%
Domestic production activities deduction		(0.00%)		(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference		0.90%		0.50%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		13.50%		(17.50%)
Production tax credits and other credits				(49.80%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent		(0.00%)		(0.00%)
Noncontrolling interests		0.00%
Other(c)		(3.60%)		(1.40%)
Effective income tax rate		47.20%		9.00%