Retirement Benefits - Assumptions Used In Calculations (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Benefit Obligation [Abstract]
Discount rate		4.80%		3.92%		4.74%
Rate of compensation increase		3.25%	[1]	3.25%	[2]	3.75%
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost [Abstract]
Expected return on plan assets	7.00%	7.50%	[3]	7.50%	[3]	8.00%	[3]
Discount rate		3.92%	[4]	3.71%	[5]	5.26%
Rate of compensation increase		3.75%	[2]	3.75%		3.75%
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Benefit Obligation [Abstract]
Discount rate		4.90%		4.00%		4.80%
Rate of compensation increase		3.25%	[1]	3.25%	[2]	3.75%
Healthcare cost trend on covered charges		6.00%		6.50%		6.50%
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost [Abstract]
Expected return on plan assets	6.59%	6.45%	[3]	6.68%	[3]	7.08%	[3]
Discount rate		4.00%	[4]	3.72%	[5]	5.30%
Rate of compensation increase		3.75%	[2]	3.75%		3.75%
Healthcare cost trend on covered charges		6.50%		6.50%		7.00%

[1] 3.25% for 2014-2018 and 3.75% thereafter.

[2] 3.25% for 2013-2017 and 3.75% thereafter

[3] Not applicable to pension and other postretirement benefit plans that do not have plan assets.

[4] The discount rates above represent the initial discount rates used to establish Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2013. Certain of the benefit plans were remeasured during the year using discount rates of 4.21% and 4.66% for pension and other postretirement benefits, respectively. Costs for the year ended December 31, 2013 reflect the impact of these remeasurements.

[5] The discount rates above represent the initial discounts rates used to establish Exelon’s pension and other postretirement benefits costs for 2012. Certain of the benefit plans were remeasured during the year due to the Constellation merger, plan settlement and curtailment events, and plan changes using discount rates of 3.71% and 3.72% for pension and other postretirement benefits, respectively. Costs for the year ended December 31, 2012 reflect the impact of these remeasurements.