Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Dec. 31, 2020 USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 2,719
Other Commitments, Due in Next Twelve Months	2,198
Other Commitment, to be Paid, Year Two	106
Other Commitment, to be Paid, Year Three	17
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	387
Guarantee obligations maximum exposure	71
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,154
Other Commitments, Due in Next Twelve Months	2,037
Other Commitment, to be Paid, Year Two	103
Other Commitment, to be Paid, Year Three	14
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	223
Other Commitments, Due in Next Twelve Months	23
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	200
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	180
Other Commitments, Due in Next Twelve Months	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	178
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
Other Commitments, Due in Next Twelve Months	5
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	50
Other Commitments, Due in Next Twelve Months	24
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	9
Guarantee obligations maximum exposure	71
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	23
Other Commitments, Due in Next Twelve Months	14
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	3
Guarantee obligations maximum exposure	24
Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	16
Other Commitments, Due in Next Twelve Months	5
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Guarantee obligations maximum exposure	30
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	11
Other Commitments, Due in Next Twelve Months	5
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	1
Other Commitment, to be Paid, after Year Five	2
Guarantee obligations maximum exposure	17
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,243
Other Commitments, Due in Next Twelve Months	1,179
Other Commitment, to be Paid, Year Two	50
Other Commitment, to be Paid, Year Three	14
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Financial Standby Letter of Credit [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,228
Other Commitments, Due in Next Twelve Months	1,164
Other Commitment, to be Paid, Year Two	50
Other Commitment, to be Paid, Year Three	14
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Financial Standby Letter of Credit [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	7
Other Commitments, Due in Next Twelve Months	7
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Financial Standby Letter of Credit [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	2
Other Commitments, Due in Next Twelve Months	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,070
Other Commitments, Due in Next Twelve Months	1,017
Other Commitment, to be Paid, Year Two	53
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	926
Other Commitments, Due in Next Twelve Months	873
Other Commitment, to be Paid, Year Two	53
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	16
Other Commitments, Due in Next Twelve Months	16
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	2
Other Commitments, Due in Next Twelve Months	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	3
Other Commitments, Due in Next Twelve Months	3
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	22
Other Commitments, Due in Next Twelve Months	22
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	14
Other Commitments, Due in Next Twelve Months	14
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	4
Other Commitments, Due in Next Twelve Months	4
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bond [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	4
Other Commitments, Due in Next Twelve Months	4
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	378
Other Commitments, Due in Next Twelve Months	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	378
Guarantee of Indebtedness of Others [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	200
Other Commitments, Due in Next Twelve Months	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	200
Guarantee of Indebtedness of Others [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	178
Other Commitments, Due in Next Twelve Months	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	178
Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	28
Other Commitments, Due in Next Twelve Months	2
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	9
Guarantee Obligations [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	28
Other Commitments, Due in Next Twelve Months	2
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five	5
Other Commitment, to be Paid, after Year Five	9
Guarantee Obligations [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
Other Commitments, Due in Next Twelve Months	0
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	3
Guarantee Obligations [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	12
Other Commitments, Due in Next Twelve Months	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Guarantee Obligations [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	7
Other Commitments, Due in Next Twelve Months	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	1
Other Commitment, to be Paid, after Year Five	$ 2
Minimum [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	22 years
Minimum [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	11 years
Minimum [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Maximum [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	82 years
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	31 years
Maximum [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	16 years
Maximum [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	82 years
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	22 years
Maximum [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	12 years
Maximum [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	5 years
Maximum [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	12 years
Maximum [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Maximum [Member] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	8 years