Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
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	1.10%	3.00%	0.50%	5.30%
Qualified nuclear decommissioning trust fund income	(0.30%)	3.50%	2.00%	3.20%
Domestic production activities deduction	(2.40%)		(2.70%)
Tax exempt income		0.20%		0.20%
Health care reform legislation	0.00%	0.10%	0.10%	0.10%
Amortization of investment tax credit, net deferred taxes	(1.00%)	(1.50%)	(1.10%)	(2.30%)
Plant basis differences	(0.80%)	(0.80%)	(1.60%)	(1.70%)
Production tax credits and other credits	1.90%	2.20%	2.10%	2.40%
Noncontrolling interest	(1.20%)		(1.40%)
Other	(0.30%)	0.50%	(1.50%)	0.20%
Effective income tax rate	28.20%	37.40%	27.20%	37.20%
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	0.70%	2.60%	(1.40%)	1.80%
Qualified nuclear decommissioning trust fund income	(0.40%)	5.30%	3.60%	5.10%
Domestic production activities deduction	(3.20%)		(4.80%)
Tax exempt income		0.30%		0.30%
Health care reform legislation	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, net deferred taxes	(1.20%)	(2.10%)	(1.70%)	(3.40%)
Plant basis differences	0.00%	0.00%	0.00%	0.00%
Production tax credits and other credits	2.40%	3.30%	3.70%	3.90%
Noncontrolling interest	(1.60%)		(2.60%)
Other	(1.40%)	0.10%	(2.50%)	1.10%
Effective income tax rate	25.50%	37.30%	21.90%	35.40%
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	5.00%	5.40%	5.00%	5.20%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Tax exempt income		0.00%		0.00%
Health care reform legislation	0.20%	0.40%	0.20%	0.90%
Amortization of investment tax credit, net deferred taxes	(0.30%)	(0.40%)	(0.30%)	(0.80%)
Plant basis differences	0.00%	(0.40%)	(0.30%)	(1.20%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interest	0.00%		0.00%
Other	0.10%	0.30%	0.10%	0.80%
Effective income tax rate	40.00%	40.30%	39.70%	39.90%
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	0.10%	(0.30%)	0.30%	1.90%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Tax exempt income		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	(11.30%)	(6.90%)	(11.00%)	(7.30%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interest	0.00%		0.00%
Other	(0.10%)	(0.10%)	0.10%	0.00%
Effective income tax rate	23.60%	27.60%	24.30%	29.50%
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	4.60%	5.60%	4.90%	5.60%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Domestic production activities deduction	0.00%		0.00%
Tax exempt income		0.00%		0.00%
Health care reform legislation	0.20%	0.20%	0.20%	0.20%
Amortization of investment tax credit, net deferred taxes	(0.30%)	(0.30%)	(0.30%)	(0.30%)
Plant basis differences	0.50%	0.10%	0.50%	(0.40%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interest	0.00%		0.00%
Other	(1.20%)	(0.20%)	(0.50%)	0.00%
Effective income tax rate	38.80%	40.40%	39.80%	40.10%