Commitments and Contingencies - Commitments Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) MW		Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Nov. 29, 2016 employee	Jun. 30, 2014 USD ($)
Guarantor Obligations [Line Items]
Commitments and Contingencies							$ 1,000.0
Power Volume | MW		220
Noncash Merger Related Costs		$ 0.0	[1],[2]	$ 503.0
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Costs Incurred, Development Costs	457.0
Consent Decree Penalty		1.6
Commitments and Contingencies
Entity Number of Employees | employee						1,500
Leasehold Improvements, Gross					110.0
Noncash Merger Related Costs		0.0	[2]	3.0
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies
Noncash Merger Related Costs				0.0
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies
Noncash Merger Related Costs				0.0
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs				$ 0.0
Nuclear Plant [Member] | Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies	450.0	450.0
Nuclear Plant [Member] | Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies	$ 500.0	$ 500.0

[1] 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.