Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Jun. 30, 2021 USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,079
Other Commitment, to be Paid, Remainder of Fiscal Year	1,210
Other Commitment, to be Paid, Year One	1,462
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	8
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	390
Guarantor Obligations, Maximum Exposure, Undiscounted	75
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,751
Other Commitment, to be Paid, Remainder of Fiscal Year	591
Other Commitment, to be Paid, Year One	1,160
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 and Beyond	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	920
Other Commitment, to be Paid, Remainder of Fiscal Year	619
Other Commitment, to be Paid, Year One	299
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	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 One	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 and Beyond	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	30
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	12
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,507
Other Commitment, to be Paid, Remainder of Fiscal Year	1,092
Other Commitment, to be Paid, Year One	1,415
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 and Beyond	0
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,735
Other Commitment, to be Paid, Remainder of Fiscal Year	578
Other Commitment, to be Paid, Year One	1,157
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 and Beyond	0
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	772
Other Commitment, to be Paid, Remainder of Fiscal Year	514
Other Commitment, to be Paid, Year One	258
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 and Beyond	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	224
Other Commitment, to be Paid, Remainder of Fiscal Year	16
Other Commitment, to be Paid, Year One	6
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	200
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	7
Other Commitment, to be Paid, Year One	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 and Beyond	0
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	9
Other Commitment, to be Paid, Year One	6
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five and Beyond	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 One	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 and Beyond	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	181
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year One	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 and Beyond	178
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year One	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 and Beyond	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 One	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 and Beyond	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	5
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	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 and Beyond	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	0
Other Commitment, to be Paid, Year One	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 and Beyond	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 One	1
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 and Beyond	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	55
Other Commitment, to be Paid, Remainder of Fiscal Year	8
Other Commitment, to be Paid, Year One	20
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	12
Guarantor Obligations, Maximum Exposure, Undiscounted	75
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	25
Other Commitment, to be Paid, Remainder of Fiscal Year	8
Other Commitment, to be Paid, Year One	17
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 and Beyond	0
Pepco Holdings LLC [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	30
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	6
Other Commitment, to be Paid, Year Four	6
Other Commitment, to be Paid, Year Five and Beyond	12
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	27
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year One	14
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five and Beyond	4
Guarantor Obligations, Maximum Exposure, Undiscounted	26
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	4
Other Commitment, to be Paid, Year One	13
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 and Beyond	0
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	10
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	2
Other Commitment, to be Paid, Year Four	2
Other Commitment, to be Paid, Year Five and Beyond	4
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	17
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	3
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five and Beyond	5
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	2
Other Commitment, to be Paid, Year One	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 and Beyond	0
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	13
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year One	1
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five and Beyond	5
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year One	3
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 and Beyond	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 One	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 and Beyond	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	0
Other Commitment, to be Paid, Year One	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 and Beyond	$ 3
Minimum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Maximum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years