Commitments and Contingencies - Litigation and Regulatory Matters (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Open_claim	Mar. 31, 2017 USD ($)
Asbestos Loss Contingency [Abstract]
Open asbestos liability claims | Open_claim	240
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve	$ 83	$ 82
Asbestos liability reserve related to open claims		23
Asbestos liability reserve related to anticipated claims		$ 59
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value	$ 14