Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Dec. 31, 2019 USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 2,714
Other Commitments, Due in Next Twelve Months	2,125
Other Commitment, Due in Second Year	189
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	6
Other Commitment, Due after Fifth Year	388
Guarantee obligations maximum exposure	69
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,110
Other Commitments, Due in Next Twelve Months	1,964
Other Commitment, Due in Second Year	146
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]
Guarantor Obligations [Line Items]
Other Commitment	257
Other Commitments, Due in Next Twelve Months	55
Other Commitment, Due in Second Year	2
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]
Guarantor Obligations [Line Items]
Other Commitment	187
Other Commitments, Due in Next Twelve Months	9
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]
Guarantor Obligations [Line Items]
Other Commitment	5
Other Commitments, Due in Next Twelve Months	5
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
Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	47
Other Commitments, Due in Next Twelve Months	23
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	6
Other Commitment, Due after Fifth Year	10
Guarantee obligations maximum exposure	69
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	23
Other Commitments, Due in Next Twelve Months	14
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	2
Other Commitment, Due after Fifth Year	5
Guarantee obligations maximum exposure	23
Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	15
Other Commitments, Due in Next Twelve Months	5
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	3
Other Commitment, Due after Fifth Year	3
Guarantee obligations maximum exposure	29
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	10
Other Commitments, Due in Next Twelve Months	4
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	1
Other Commitment, Due after Fifth Year	2
Guarantee obligations maximum exposure	18
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,455
Other Commitments, Due in Next Twelve Months	1,314
Other Commitment, Due in Second Year	141
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
Financial Standby Letter of Credit [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,440
Other Commitments, Due in Next Twelve Months	1,302
Other Commitment, Due in Second Year	138
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
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, 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
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, 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
Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	855
Other Commitments, Due in Next Twelve Months	809
Other Commitment, Due in Second Year	46
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 Bond [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	670
Other Commitments, Due in Next Twelve Months	662
Other Commitment, Due in Second Year	8
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 Bond [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	50
Other Commitments, Due in Next Twelve Months	48
Other Commitment, Due in Second Year	2
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 Bond [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
Other Commitments, Due in Next Twelve Months	9
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
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, 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
Surety Bond [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	21
Other Commitments, Due in Next Twelve Months	21
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
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, 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
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, 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
Surety Bond [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	3
Other Commitments, Due in Next Twelve Months	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
Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	378
Other Commitments, Due in Next Twelve Months	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
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, 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
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, 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
Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	26
Other Commitments, Due in Next Twelve Months	2
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	6
Other Commitment, Due after Fifth Year	10
Guarantee Obligations [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Other Commitment	26
Other Commitments, Due in Next Twelve Months	2
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	6
Other Commitment, Due after Fifth Year	10
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, 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	2
Other Commitment, Due after Fifth Year	5
Guarantee Obligations [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	11
Other Commitments, Due in Next Twelve Months	1
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	3
Other Commitment, Due after Fifth Year	3
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, 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	1
Other Commitment, Due after Fifth Year	$ 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	23 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	12 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	83 years
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	32 years
Maximum [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	17 years
Maximum [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	83 years
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	23 years
Maximum [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	13 years
Maximum [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	6 years
Maximum [Member] | Delmarva Power & Light Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	13 years
Maximum [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	2 years
Maximum [Member] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Lessor, Operating Lease, Term of Contract	8 years