Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Jun. 30, 2020 USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,599
Other Commitment, to be Paid, Remainder of Fiscal Year	1,026
Other Commitment, to be Paid, Year Two	1,153
Other Commitment, to be Paid, Year Three	21
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	7
Other Commitment, to be Paid, after Year Five	389
Guarantor Obligations, Maximum Exposure, Undiscounted	74
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,291
Other Commitment, to be Paid, Remainder of Fiscal Year	475
Other Commitment, to be Paid, Year Two	816
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 Bonds
Other Commitments [Line Items]
Other Commitment	902
Other Commitment, to be Paid, Remainder of Fiscal Year	550
Other Commitment, to be Paid, Year Two	335
Other Commitment, to be Paid, Year Three	17
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
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Other Commitment, to be Paid, Remainder of Fiscal Year	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
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	28
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	7
Other Commitment, to be Paid, after Year Five	11
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,030
Other Commitment, to be Paid, Remainder of Fiscal Year	946
Other Commitment, to be Paid, Year Two	1,067
Other Commitment, to be Paid, Year Three	17
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
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,276
Other Commitment, to be Paid, Remainder of Fiscal Year	467
Other Commitment, to be Paid, Year Two	809
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
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	754
Other Commitment, to be Paid, Remainder of Fiscal Year	479
Other Commitment, to be Paid, Year Two	258
Other Commitment, to be Paid, Year Three	17
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]
Other Commitments [Line Items]
Other Commitment	222
Other Commitment, to be Paid, Remainder of Fiscal Year	12
Other Commitment, to be Paid, Year Two	10
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
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year Two	3
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
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	15
Other Commitment, to be Paid, Remainder of Fiscal Year	8
Other Commitment, to be Paid, Year Two	7
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
Commonwealth Edison Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Other Commitment, to be Paid, Remainder of Fiscal Year	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
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	184
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year Two	2
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
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	6
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year Two	2
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
PECO Energy Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
Other Commitment, to be Paid, Remainder of Fiscal Year	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
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	5
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year Two	1
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
Baltimore Gas and Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	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
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	1
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]
Other Commitments [Line Items]
Other Commitment	50
Other Commitment, to be Paid, Remainder of Fiscal Year	7
Other Commitment, to be Paid, Year Two	18
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	7
Other Commitment, to be Paid, after Year Five	11
Guarantor Obligations, Maximum Exposure, Undiscounted	72
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	22
Other Commitment, to be Paid, Remainder of Fiscal Year	6
Other Commitment, to be Paid, Year Two	16
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] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	28
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	4
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	7
Other Commitment, to be Paid, after Year Five	11
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	14
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	4
Guarantor Obligations, Maximum Exposure, Undiscounted	25
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	14
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	13
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
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	9
Other Commitment, to be Paid, Remainder of Fiscal Year	0
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	2
Other Commitment, to be Paid, after Year Five	4
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	16
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	4
Other Commitment, to be Paid, after Year Five	4
Guarantor Obligations, Maximum Exposure, Undiscounted	31
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	1
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
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	12
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	4
Other Commitment, to be Paid, after Year Five	4
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	2
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	3
Guarantor Obligations, Maximum Exposure, Undiscounted	18
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	2
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
Atlantic City Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	0
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	$ 3
Maximum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years
Minimum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year