Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 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	(2.70%)	(3.40%)	(3.10%)	(2.00%)
Qualified nuclear decommissioning trust fund income	(5.40%)	(0.30%)	(0.90%)	2.00%
Domestic production activities deduction	(4.90%)	(2.40%)	(2.80%)	(2.70%)
Health care reform legislation	(0.00%)	(0.00%)	(0.00%)	(0.10%)
Amortization of investment tax credit, net deferred taxes	(2.30%)	(1.00%)	(1.20%)	(1.10%)
Plant basis differences	(1.40%)	(0.80%)	(1.20%)	(1.60%)
Production tax credits and other credits	(3.80%)	(1.90%)	(2.20%)	(2.10%)
Statute of limitations expiration	(6.40%)	(3.80%)	(1.60%)	(2.50%)
Noncontrolling interest	1.70%	(1.20%)	(0.00%)	(1.40%)
Other	1.20%	1.20%	0.90%	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	16.40%	28.20%	29.10%	27.20%
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	(2.10%)	(3.70%)	(2.80%)	(1.20%)
Qualified nuclear decommissioning trust fund income	(12.50%)	(0.40%)	(1.60%)	3.60%
Domestic production activities deduction	(11.60%)	(3.20%)	(4.90%)	(4.80%)
Health care reform legislation	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Amortization of investment tax credit, net deferred taxes	(5.20%)	(1.20%)	(1.90%)	(1.70%)
Plant basis differences	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Production tax credits and other credits	(9.00%)	(2.40%)	(3.80%)	(3.70%)
Statute of limitations expiration	(15.20%)	(5.00%)	(2.90%)	(4.40%)
Noncontrolling interest	3.90%	(1.60%)	0.10%	(2.60%)
Other	0.40%	0.60%	0.60%	(0.70%)
Effective Income Tax Rate Reconciliation, Percent	(12.10%)	25.50%	23.40%	21.90%
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%)	(5.00%)	(5.20%)	(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%)	(0.00%)	(0.10%)	(0.30%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	0.30%	0.10%	0.20%	0.10%
Effective Income Tax Rate Reconciliation, Percent	39.90%	40.00%	40.00%	39.70%
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	(1.20%)	(0.10%)	(1.20%)	(0.30%)
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	(7.00%)	(11.30%)	(7.30%)	(11.00%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	0.00%	(0.10%)	0.20%	0.10%
Effective Income Tax Rate Reconciliation, Percent	29.10%	23.60%	29.00%	24.30%
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%)	(4.60%)	(5.30%)	(4.90%)
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	(0.20%)	(0.20%)	(0.20%)	(0.20%)
Amortization of investment tax credit, net deferred taxes	(0.20%)	(0.30%)	(0.10%)	(0.30%)
Plant basis differences	(0.60%)	0.50%	(0.40%)	0.50%
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	(0.40%)	(1.20%)	(0.10%)	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	39.30%	38.80%	39.90%	39.80%