Commitments and Contingencies - Litigation and Regulatory Matters (Details) $ in Millions	3 Months Ended
	Sep. 30, 2016 USD ($) claimant Open_claim	Dec. 31, 2015 USD ($)
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve	$ 22	$ 0
Asbestos liability reserve related to open claims	$ 0
Open asbestos liability claims | Open_claim	61,000,000
Asbestos liability reserve related to anticipated claims	$ 95
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency Accrual	44
Loss Contingency, Damages Sought, Value	$ 14
Baltimore Gas and Electric Company [Member]
Asbestos Loss Contingency [Abstract]
Number of claimants | claimant	83,000,000