Income Taxes - Reconciliation to Effective Tax Rate (Details)		3 Months Ended			6 Months Ended
	Mar. 31, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(2.30%)		(3.90%)	(0.80%)	(3.20%)
Domestic production activities deduction		(0.00%)		2.00%	(0.00%)	2.10%
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		1.80%		0.60%	1.70%	0.80%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(6.90%)		(1.00%)	(6.30%)	(1.10%)
Production tax credits and other credits		(5.70%)		1.00%	(5.60%)	(0.60%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent		(5.80%)		(1.30%)	(5.50%)	(1.60%)
Noncontrolling interests		0.90%		(0.40%)	0.70%	(0.60%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		(1.70%)			(1.00%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.20%			14.50%
Other(c)		3.30%		(1.40%)	2.80%	(0.80%)
Effective income tax rate		24.60%		34.00%	39.30%	33.40%
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%
State income taxes, net of Federal income tax benefit(b)		116.70%		(3.40%)	(2.60%)	(3.00%)
Domestic production activities deduction		(0.00%)		3.40%	(0.00%)	3.40%
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		157.80%		0.90%	2.50%	1.10%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		0.00%		0.00%	0.00%	0.00%
Production tax credits and other credits		(591.20%)		1.70%	(9.80%)	(0.90%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent		(603.00%)		(2.20%)	(9.60%)	(2.50%)
Noncontrolling interests		94.40%		(0.60%)	1.20%	(0.80%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		(410.80%)			(3.90%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.00%			0.00%
Other(c)		52.30%		(2.00%)	3.80%	(0.60%)
Effective income tax rate		(620.00%)		31.60%	28.80%	31.70%
Commonwealth Edison Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(4.80%)		(5.60%)	(4.90%)	(5.30%)
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		0.20%		0.30%	0.20%	0.30%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(0.40%)		(0.10%)	(0.30%)	(0.20%)
Production tax credits and other credits		(0.00%)		(0.00%)	(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%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.00%			0.00%
Other(c)		0.60%		(0.50%)	0.10%	(0.40%)
Effective income tax rate		38.60%		40.70%	39.30%	40.20%
PECO Energy Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(0.30%)		(1.40%)	(0.70%)	(1.30%)
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		(11.30%)		(9.00%)	(10.20%)	(7.50%)
Production tax credits and other credits		(0.00%)		(0.00%)	(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%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.00%			0.00%
Other(c)		5.20%		(0.50%)	2.40%	(0.20%)
Effective income tax rate		18.70%		27.80%	23.00%	28.90%
Baltimore Gas and Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(2.00%)		(5.30%)	(4.60%)	(5.30%)
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%		0.10%	0.00%	0.20%
Amortization of investment tax credit, including deferred taxes on basis difference		0.40%		0.20%	0.10%	0.10%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(20.60%)		(0.50%)	(4.50%)	(0.30%)
Production tax credits and other credits		(0.00%)		(0.00%)	(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%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.00%			0.00%
Other(c)		1.00%		(0.80%)	(0.10%)	(0.00%)
Effective income tax rate		15.00%		40.50%	35.10%	40.10%
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%
State income taxes, net of Federal income tax benefit(b)				(5.30%)		(6.40%)
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				0.30%		0.40%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(7.30%)		(6.10%)
Production tax credits and other credits				(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				0.00%		0.00%
Noncontrolling interests						0.00%
Other(c)				(1.10%)		0.30%
Effective income tax rate				33.80%		34.60%
Pepco Holdings LLC [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%
State income taxes, net of Federal income tax benefit(b)		(6.10%)
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		0.30%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(7.00%)
Production tax credits and other credits		(0.00%)
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%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		1.00%
Other(c)		(1.00%)
Effective income tax rate		35.80%
Delmarva Power and Light Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(4.80%)		(5.00%)	5.20%	(5.50%)
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		0.60%		1.00%	(0.40%)	0.40%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(3.50%)		(4.20%)	2.00%	(1.50%)
Production tax credits and other credits		(0.00%)		(0.00%)	(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%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		3.10%			(30.50%)
Other(c)		(1.20%)		(3.70%)	0.10%	(0.80%)
Effective income tax rate		40.00%		38.50%	1.60%	39.40%
Potomac Electric Power Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(3.50%)		(5.00%)	9.50%	(4.10%)
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		0.10%		(0.00%)	(0.10%)	(0.00%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(5.70%)		(8.30%)	12.60%	(8.20%)
Production tax credits and other credits		(0.00%)		(0.00%)	(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%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		0.00%			0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent		0.20%			(36.10%)
Other(c)		1.00%		1.70%	0.50%	0.30%
Effective income tax rate		31.90%		30.00%	1.60%	30.60%
Atlantic City Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%		35.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit(b)		(5.90%)		(9.90%)	(5.90%)	(5.50%)
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		1.60%		0.20%	(0.10%)	0.90%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(7.10%)		(0.10%)	1.00%	(1.70%)
Production tax credits and other credits		(0.00%)		(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				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, Nondeductible Expense, Other, Percent					(17.70%)
Other(c)		(7.80%)		4.60%	0.10%	0.40%
Effective income tax rate		40.00%		40.00%	24.20%	37.50%
Atlantic City Electric Company [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate	35.00%		35.00%
State income taxes, net of Federal income tax benefit(b)	(5.20%)		(11.90%)
Domestic production activities deduction	(0.00%)		(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)		0.90%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	1.70%		(13.50%)
Production tax credits and other credits	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	0.00%		0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent	(18.90%)		11.10%
Other(c)	(0.00%)		(3.60%)
Effective income tax rate	23.10%		47.20%