Retirement Benefits - Contributions made to Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions			12 Months Ended
	Mar. 02, 2022	Feb. 01, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			$ 129	$ 616	$ 665
Expected qualified pension plan contributions			93
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			15
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			47
Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			41	184	196
Expected qualified pension plan contributions			3
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			1
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			18
PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			1	18	18
Expected qualified pension plan contributions			2
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			1
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			1
Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			19	68	81
Expected qualified pension plan contributions			17
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			1
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			14
Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			24	78	48
Expected qualified pension plan contributions			66
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			8
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			11
Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			12	11	11
Expected qualified pension plan contributions			0
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			1
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			10
Delmarva Power & Light Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			4	1	1
Expected qualified pension plan contributions			0
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			0
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			0
Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			3	7	3
Expected qualified pension plan contributions			7
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months			0
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year			0
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	$ 33	$ 207	75	570	343
Pension Plan, Defined Benefit [Member] | Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			24	176	174
Pension Plan, Defined Benefit [Member] | PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			1	15	17
Pension Plan, Defined Benefit [Member] | Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			0	48	57
Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			8	69	39
Pension Plan, Defined Benefit [Member] | Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			1	3	2
Pension Plan, Defined Benefit [Member] | Delmarva Power & Light Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			2	1	1
Pension Plan, Defined Benefit [Member] | Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			0	7	3
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			54	42	63
Other Postretirement Benefit Plan, Defined Benefit [Member] | Commonwealth Edison Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			17	8	22
Other Postretirement Benefit Plan, Defined Benefit [Member] | PECO Energy Co
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			0	3	1
Other Postretirement Benefit Plan, Defined Benefit [Member] | Baltimore Gas and Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			19	20	24
Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			16	9	9
Other Postretirement Benefit Plan, Defined Benefit [Member] | Potomac Electric Power Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			11	8	9
Other Postretirement Benefit Plan, Defined Benefit [Member] | Delmarva Power & Light Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			2	0	0
Other Postretirement Benefit Plan, Defined Benefit [Member] | Atlantic City Electric Company
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions			$ 3	$ 0	$ 0