Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Mar. 31, 2020 USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,718
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,779
Other Commitment, Due in Second Year	537
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	383
Guarantor Obligations, Maximum Exposure, Undiscounted	72
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,464
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,080
Other Commitment, Due in Second Year	384
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	849
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	698
Other Commitment, Due in Second Year	151
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	27
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,134
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,662
Other Commitment, Due in Second Year	472
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,449
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,071
Other Commitment, Due in Second Year	378
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	685
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	591
Other Commitment, Due in Second Year	94
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	222
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	15
Other Commitment, Due in Second Year	7
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	200
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	4
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	15
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	11
Other Commitment, Due in Second Year	4
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	187
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	8
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	178
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	9
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	8
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
PECO Energy Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	19
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	18
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Baltimore Gas and Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	2
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	16
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	48
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	21
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Guarantor Obligations, Maximum Exposure, Undiscounted	72
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	21
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	20
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Pepco Holdings LLC [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	27
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	14
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	4
Other Commitment, Due after Fifth Year	2
Guarantor Obligations, Maximum Exposure, Undiscounted	24
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	14
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	14
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	9
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	4
Other Commitment, Due after Fifth Year	2
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	15
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	2
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	5
Other Commitment, Due after Fifth Year	2
Guarantor Obligations, Maximum Exposure, Undiscounted	30
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	11
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	2
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	5
Other Commitment, Due after Fifth Year	2
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	4
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	1
Guarantor Obligations, Maximum Exposure, Undiscounted	18
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Atlantic City Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	7
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	$ 1
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