Commitments and Contingencies - Schedule of Commercial Commitments (Details) - USD ($) $ in Millions	Mar. 31, 2016	Jul. 31, 2014
Guarantor Obligations [Line Items]
Other Commitment	$ 6,282
Guarantor Obligations, Maximum Exposure, Undiscounted	53
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,628
Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	628
Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	950
Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	3,056
GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	20
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	5,468	$ 91
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,560
Exelon Generation Co L L C [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Exelon Generation Co L L C [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	852
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	3,056
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	226
Commonwealth Edison Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	16
Commonwealth Edison Co [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	200
Commonwealth Edison Co [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	10
Commonwealth Edison Co [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	209
PECO Energy Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	22
PECO Energy Co [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	178
PECO Energy Co [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
PECO Energy Co [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	262
Baltimore Gas and Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	2
Baltimore Gas and Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	250
Baltimore Gas and Electric Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	10
Baltimore Gas and Electric Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
PEPCO Holdings Inc [Member]
Guarantor Obligations [Line Items]
Other Commitment	37
PEPCO Holdings Inc [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1
PEPCO Holdings Inc [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
PEPCO Holdings Inc [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	16
PEPCO Holdings Inc [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
PEPCO Holdings Inc [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	20
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	15
Guarantor Obligations, Maximum Exposure, Undiscounted	13
Potomac Electric Power Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
Potomac Electric Power Company [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	6
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	8
Guarantor Obligations, Maximum Exposure, Undiscounted	14
Atlantic City Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	4
Atlantic City Electric Company [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	12
Guarantor Obligations, Maximum Exposure, Undiscounted	17
Delmarva Power and Light Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	3
Delmarva Power and Light Company [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	$ 8