Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	3.90%	2.10%	3.20%	(0.60%)
Qualified nuclear decommissioning trust fund income	(1.00%)	4.10%	0.60%	5.90%
Domestic production activities deduction	(2.00%)	(2.00%)	(2.10%)	(3.20%)
Health care reform legislation	0.00%	0.00%	0.00%	0.10%
Amortization of investment tax credit, net deferred taxes	(0.60%)	(0.40%)	(0.80%)	(1.20%)
Plant basis differences	(1.00%)	(1.60%)	(1.10%)	(3.00%)
Production tax credits and other credits	1.30%	0.80%	1.60%	2.40%
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	(0.40%)	(2.00%)	(0.60%)	(1.90%)
Other	1.40%	(1.20%)	0.80%	(3.10%)
Effective income tax rate	34.00%	33.20%	33.40%	25.60%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	3.40%	1.70%	3.00%	(14.70%)
Qualified nuclear decommissioning trust fund income	(1.70%)	6.00%	0.90%	27.70%
Domestic production activities deduction	(3.40%)	(2.90%)	(3.40%)	(14.80%)
Health care reform legislation	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, net deferred taxes	(0.90%)	(0.50%)	(1.10%)	(4.90%)
Plant basis differences	0.00%	0.00%	0.00%	0.00%
Production tax credits and other credits	2.20%	1.10%	2.50%	11.10%
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	(0.60%)	(2.90%)	(0.80%)	(8.80%)
Other	2.00%	(0.40%)	0.60%	(8.90%)
Effective income tax rate	31.60%	34.90%	31.70%	(0.50%)
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.60%	4.60%	5.30%	5.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Health care reform legislation	0.00%	0.20%	0.00%	0.20%
Amortization of investment tax credit, net deferred taxes	(0.30%)	(0.30%)	(0.30%)	(0.30%)
Plant basis differences	(0.10%)	(0.40%)	(0.20%)	(0.50%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.50%	0.20%	0.40%	0.20%
Effective income tax rate	40.70%	39.30%	40.20%	39.60%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	1.40%	(0.50%)	1.30%	0.40%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Health care reform legislation	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, net deferred taxes	(0.10%)	(0.10%)	(0.10%)	(0.10%)
Plant basis differences	(9.00%)	(13.20%)	(7.50%)	(10.80%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.50%	0.30%	0.20%	0.30%
Effective income tax rate	27.80%	21.50%	28.90%	24.80%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.30%	4.10%	5.30%	5.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Health care reform legislation	0.10%	0.20%	0.20%	0.20%
Amortization of investment tax credit, net deferred taxes	(0.20%)	(0.70%)	(0.10%)	(0.30%)
Plant basis differences	(0.50%)	5.10%	(0.30%)	0.40%
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.80%	(1.30%)	0.00%	0.10%
Effective income tax rate	40.50%	42.40%	40.10%	40.40%