Commitments and Contingencies - Commitments Narrative (Details) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2016 USD ($)	Jun. 30, 2016 USD ($) MW	Jun. 30, 2015 USD ($)	Jun. 30, 2013 USD ($)
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 50	$ 50
Noncash Merger Related Costs	[1],[2]		503
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs	[2]		3
Costs Incurred, Development Costs		402
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement					$ 1,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Construction Cost				$ 95
Business Acquisition, Development Of New Generation Cost		500	$ 500
Business Acquisition, Expected New Generation Mwh | MW			275
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Construction Cost				$ 120
Business Acquisition, Development Of New Generation Cost		600	$ 600
Business Acquisition, Expected New Generation Mwh | MW			300
Noncash Merger Related Costs			$ 105
Equity Unit Purchase Agreements [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
2015		$ 22	$ 22

[1] (e)Excludes $5 million of forgiveness of Accounts receivable related to merger commitments recorded in connection with the PHI Merger, the balance is included within Provision for uncollectible accounts.

[2] See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI.