Nuclear Decommissioning (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear Decommissioning Annual Recovery Current	$ 24
Half Of Non Decommissioning Withdraw	50.00%exc_HalfOfNonDecommissioningWithdraw
Decommissioning Fund Investments	10,712us-gaap_DecommissioningFundInvestments	10,537us-gaap_DecommissioningFundInvestments
Decommissioning Liability, Noncurrent	136	155
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Shortfall	50
Decommissioning Shortfall Percentage	5.00%
Decommissioning Fund Investments	10,712	10,537
Decommissioning Liability, Noncurrent	136	155
Nuclear Plant [Member] \| Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent	$ 87

Amount of decommissioning shortfall with recourse for collection from customers.

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- Definition

Percent of additional decommissioning shortfall with recourse for collection from customers.

+ References

No definition available.

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- Definition

Half Of Non Decommissioning Withdraw

+ References

No definition available.

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- Definition

Current annual recovery of nuclear decommissioning costs from customers filed with state regulator

+ References

No definition available.

+ Details

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- Definition

Decommission fund to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Decommission fund investment for the process whereby a power station, at the end of its economic life, is taken permanently out of service and its site made available for other purposes. In the case of a nuclear station this comprises three different states of clearance. Immediately after the final closure, radioactive material such as nuclear fuel and operational waste is removed and the buildings surrounding the reactor shield are dismantled and finally the reactor itself is dismantled.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.12)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount of a decommissioning liability associated with a legal obligation that a firm incurs when it constructs or operates an asset that must eventually be withdrawn from active service. This may include operating assets such as nuclear power plants or shipping vessels.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q2)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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