Commitments and Contingencies - Litigation and Regulatory Matters (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) Open_claim
Asbestos Loss Contingency [Abstract]
Open asbestos liability claims | Open_claim		224
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Liability for Asbestos and Environmental Claims, Gross	$ 81	$ 83
Liability for Asbestos and Environmental Claims, Net, Payment for Claims	59
Liability for Asbestos and Environmental Claims, Net	$ 21
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value		$ 14