Income Taxes - Reconciliation to Effective Tax Rate (Details)				3 Months Ended
		Mar. 31, 2016		Mar. 31, 2017	Mar. 31, 2016		Mar. 23, 2016
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				0.90%	(1.10%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				3.40%	5.60%
Amortization of investment tax credit, including deferred taxes on basis difference				(0.40%)	(1.60%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(2.40%)	(5.50%)
Production tax credits and other credits				(0.60%)	(5.10%)
Noncontrolling interests				(0.10%)	0.50%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(11.40%)	33.60%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				(6.60%)
Other				(0.00%)	(2.00%)
Effective income tax rate				17.80%	59.40%
Exelon Generation Co L L C [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				1.00%	3.70%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				7.60%	4.20%
Amortization of investment tax credit, including deferred taxes on basis difference				(0.70%)	(1.00%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				0.00%	0.00%
Production tax credits and other credits				(1.40%)	(3.90%)
Noncontrolling interests				(0.30%)	0.30%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(3.30%)	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				(14.50%)
Other				(0.10%)	(1.60%)
Effective income tax rate				23.30%	36.70%
Commonwealth Edison Co [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				4.90%	5.10%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, 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				(0.20%)	(0.10%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				(0.00%)	0.40%
Effective income tax rate				39.50%	40.10%
PECO Energy Co [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				0.10%	1.00%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(13.20%)	(9.30%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				0.30%	(0.90%)
Effective income tax rate				22.10%	25.70%
Baltimore Gas and Electric Company [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				5.20%	5.20%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(0.90%)	(0.60%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				(0.20%)	(0.00%)
Effective income tax rate				39.00%	39.50%
Delmarva Power and Light Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				5.30%	(2.70%)	[1],[2]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)	[1]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.30%)	0.10%	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(1.90%)	0.70%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(21.90%)	(22.10%)
Other				(0.00%)	0.10%	[1]
Effective income tax rate				16.20%	11.10%	[1]
Potomac Electric Power Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				4.60%	(2.50%)	[1],[2]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	[1]				(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.00%)	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(5.80%)	2.80%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(34.20%)	(16.50%)
Other				0.50%	(0.00%)	[1]
Effective income tax rate				0.00%	18.80%	[1]
Potomac Electric Power Company [Member] | Successor [Member]
Increase (decrease) due to:
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)
Atlantic City Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				5.60%	5.90%	[1]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)	[1]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.40%)	0.20%	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(3.40%)	0.60%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(167.10%)	(17.00%)
Other				(3.00%)	0.10%	[1]
Effective income tax rate				(133.30%)	24.80%	[1]
Pepco Holdings LLC [Member] | Predecessor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate							35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent							11.90%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent							(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference							(0.90%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent							(13.50%)
Production tax credits and other credits							(0.00%)
Noncontrolling interests							0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent							11.10%
Other							3.60%
Effective income tax rate							47.20%
Pepco Holdings LLC [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%	[1]	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		5.40%	[1]	4.90%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent		(0.00%)	[1]	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference		(0.00%)	[1]	(0.20%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		0.00%	[1]	(3.80%)
Production tax credits and other credits		(0.00%)	[1]	(0.00%)
Noncontrolling interests		0.00%	[1]	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent		(15.10%)		(42.40%)
Other		0.20%	[1]	(0.40%)
Effective income tax rate		25.50%	[1]	(6.90%)

[1] Pepco, DPL and ACE recognized a loss before income taxes for the three months ended March 31, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through March 31, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.

[2] Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.