Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Jun. 30, 2019 USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,211
Guarantor Obligations, Maximum Exposure, Undiscounted	68
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,315
Surety Bonds
Other Commitments [Line Items]
Other Commitment	1,492
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	26
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,554
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,283
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	1,271
Exelon Generation Co L L C [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Exelon Generation Co L L C [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	259
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	52
Commonwealth Edison Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Commonwealth Edison Co [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	0
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	187
PECO Energy Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	0
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	9
PECO Energy Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
PECO Energy Co [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	0
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	26
Baltimore Gas and Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	9
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Baltimore Gas and Electric Company [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Baltimore Gas and Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	75
Pepco Holdings LLC [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	10
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	39
Pepco Holdings LLC [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	26
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	50
Guarantor Obligations, Maximum Exposure, Undiscounted	23
Potomac Electric Power Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	10
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	31
Potomac Electric Power Company [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	9
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	15
Guarantor Obligations, Maximum Exposure, Undiscounted	28
Delmarva Power and Light Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Delmarva Power and Light Company [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	11
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Guarantor Obligations, Maximum Exposure, Undiscounted	17
Atlantic City Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Atlantic City Electric Company [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	$ 7
Maximum [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	84 years
Maximum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years
Maximum [Member] | Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	33 years
Maximum [Member] | Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	18 years
Maximum [Member] | PECO Energy Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	84 years
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	24 years
Maximum [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	14 years
Maximum [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	7 years
Maximum [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	14 years
Maximum [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	3 years
Minimum [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | PECO Energy Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	24 years
Minimum [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	2 years
Minimum [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	13 years
Minimum [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year