The amount remitted to variable interest entities for rate stabilization bonds.

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Megawatts acquired upon completion of the acquisition.

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Note Receivable

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The number of variable interest entities (VIEs) consolidated.

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The number of variable interest entities (VIEs) not consolidated.

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Number of Project Entities with Noncontrolling Interests

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Ownership Interest in Project Entities

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Percentage of ownership interest in certain nonconsolidated VIEs where none of the equity holders consolidate these VIEs.

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Ownership Percentage of Noncontrolling Interests in Project Entities

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Projects with economic interest that is significantly greater than its stated power to direct activities of the project.

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This element represents the percentage of nuclear output to be purchased by third party.

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Represents the required purchases of power from a related party, that is not sold to third parties, over the specified term of a power purchase agreement, percent.

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No definition available.

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Amount charged against earnings in the period for a specified incurred and estimated severance cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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No definition available.

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In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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For an unclassified balance sheet, amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

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Amount of equity, excluding noncontrolling interest, attributable to the equity method investment of the entity.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Variable Interest Entities - Narrative (Details) $ in Millions		9 Months Ended	12 Months Ended
	Apr. 01, 2014 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) VIE project MW	Dec. 31, 2014 USD ($) VIE	Dec. 31, 2013 USD ($)	Jun. 09, 2015 USD ($)	Jul. 18, 2014 USD ($)
Variable Interest Entity [Line Items]
Note Receivable		$ 27
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of variable interest entities not consolidated by equity holders \| VIE			8	6
Number of variable interest entities consolidated \| VIE			7	6
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided			$ 75
Required purchases of power from CENG's nuclear plants not sold to third parties			85.00%
Purchase of nuclear output by EDF			49.99%
Guarantee obligations maximum exposure			$ 9,206
Other Severance Charges [Member]
Consolidated Variable Interest Entity [Abstract]
Severance charges recorded			6
Constellation Energy Nuclear Group [Member] \| Financial Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure	$ 165
Constellation Energy Nuclear Group [Member] \| Payment Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Due to affiliate	$ 245
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests			250				$ 91
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests			172
Exelon Generation Co L L C [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided			$ 12
Ownership Percentage Of Consolidated Variable Interest Entities			100.00%
Debt and Capital Lease Obligations			$ 8,869	$ 7,582
Wind project entities with noncontrolling equity interests \| project			9
Noncontrolling equity interest ownership percentage held by third parties			1.00%
Number of projects with significant economic power \| project			8
Ownership interests in project entities			99.00%
Ownership interest			50.01%
Required purchases of power from CENG's nuclear plants not sold to third parties	85.00%
Severance charges recorded			$ 1
Purchase of nuclear output by EDF	49.99%
Guarantee obligations maximum exposure			6,832
Exelon Generation Co L L C [Member] \| Constellation Energy Nuclear Group [Member]
Consolidated Variable Interest Entity [Abstract]
Due from affiliates	$ 400		300
Exelon Generation Co L L C [Member] \| Constellation Energy Nuclear Group [Member] \| Payment Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Due to affiliate	205
Exelon Generation Co L L C [Member] \| Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests			78
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided			$ 275
Exelon Generation Co L L C [Member] \| Solar Project Limited Liability Companies [Member]
Consolidated Variable Interest Entity [Abstract]
Business Acquisitions, Megawatts Acquired \| MW			242
Ownership Percentage Of Consolidated Variable Interest Entities			100.00%
Debt and Capital Lease Obligations			$ 655
Exelon Generation Co L L C [Member] \| AGE Biomass project [Member]
Consolidated Variable Interest Entity [Abstract]
Ownership Percentage Of Consolidated Variable Interest Entities			100.00%
Ownership interests in project entities			90.00%
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided	7		$ 7			$ 275
Remeasurement gain from derecognition of equity method investment	$ 261
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Equity Method Investment Variable Interest Entities [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided			637
Baltimore Gas and Electric Company [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure			262
Baltimore Gas and Electric Company [Member] \| RSB Bond Co LLC [Member]
Consolidated Variable Interest Entity [Abstract]
Remittance of payments received from customers for rate stabilization to BondCo.			$ 86	$ 85	$ 83