Commitments and Contingencies - Schedule of Environmental Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 429	$ 369
Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	325	301
Exelon Generation Co L L C [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	72	63
Exelon Generation Co L L C [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	0	0
Commonwealth Edison Co [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	292	266
Commonwealth Edison Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	291	264
PECO Energy Co [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	33	37
PECO Energy Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	31	35
Baltimore Gas and Electric Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	3
Baltimore Gas and Electric Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	2
Pepco Holdings LLC [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	30	33
Pepco Holdings LLC [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Potomac Electric Power Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	27	24
Potomac Electric Power Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	0	0
Delmarva Power and Light Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	3
Delmarva Power and Light Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Atlantic City Electric Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Atlantic City Electric Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 0	$ 0