Historical five-year annual average after-tax return on NDT funds

No definition available.

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- Definition

Percent of annual average accretion of the ARO used in the NRC minimum funding requirements.

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of decommissioning shortfall with recourse for collection from customers.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Estimated annual after-tax return on NDT funds used in the NRC minimum funding requirements.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Assumed term (in years) for license renewal extensions.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of years that measurement of the obligation at the present value of the future estimated costs and an annual average accretion of the ARO occurs.

+ References

No definition available.

+ Details

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Namespace Prefix:	exc_
Data Type:	xbrli:durationItemType
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Period Type:	duration

- Definition

The interest rate for investments that have an interest rate. For fixed rate investments, this indicates the fixed interest rate. If the investment has a variable interest rate, the rate stated here may be the rate that is currently relevant. In this case the "Investment, Interest Rate is Current Rate for Variable Rate Investment Flag", "Investment, Interest Rate is Discount Rate at Purchase Flag", "Investment, Interest Rate Reflects Current Yield Flag" should be used. If one of these flags are not appropriate to explain the interest rate that is indicated, then a new flag should be added or an explanation should be included in "Investment, Additional Information".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

+ Details

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Balance Type:	na
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- Definition

Amount of increase (decrease) in asset retirement obligations.

+ References

+ Details

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- Definition

Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 35
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6392603&loc=d3e7123-110846

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Balance Type:	credit
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- Definition

Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

+ Details

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Balance Type:	credit
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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

+ Details

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Balance Type:	debit
Period Type:	instant

- 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

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

- Definition

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Cash receipts from customers during the current period which are usually for sales of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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Balance Type:	debit
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- Definition

Provision for the disposal costs of spent nuclear fuel from generating stations.

+ References

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- Details

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- Details

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Asset Retirement Obligations - Narrative (Details) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2016
Asset Retirement Obligations [Line Items]
Asset Retirement Obligations, Noncurrent	$ 10,029,000,000					$ 10,029,000,000	$ 9,111,000,000
Percent of additional decommissioning shortfall with recourse	50.00%					50.00%
Nuclear decommissioning trust funds	$ 13,272,000,000					$ 13,272,000,000	11,061,000,000
Spent Nuclear Fuel Obligation, Noncurrent	1,147,000,000					1,147,000,000	1,024,000,000
Line of credit facility, maximum borrowing capacity								$ 98
Decommissioning Liability, Noncurrent	0					0	14,000,000
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)	180,000,000		$ 165,000,000		$ 288,000,000		488,000,000
Asset Retirement Obligations, Noncurrent	9,844,000,000					9,844,000,000	8,922,000,000
Asset Retirement Obligation, Revision of Estimate					$ 61,000,000	1,000,000	1,000,000
Shortfall of decommissioning funds with recourse	$ 50,000,000					$ 50,000,000
Percent of additional decommissioning shortfall with recourse	5.00%					5.00%
Nuclear decommissioning trust funds	$ 13,272,000,000					$ 13,272,000,000	11,061,000,000
Spent Nuclear Fuel Obligation, Noncurrent	1,147,000,000					1,147,000,000	1,024,000,000
ZionSolutions rent payable						1.00
Line of credit facility, maximum borrowing capacity	200,000,000					$ 200,000,000
Annual average accretion of the ARO						5.00%
Number of years used in present value measurement						30 years
Historical five-year annual average after-tax return on NDT funds						8.00%
Decommissioning Liability, Noncurrent	$ 0					$ 0	14,000,000
Exelon Generation Co L L C [Member] \| Minimum [Member]
Asset Retirement Obligations [Line Items]
Investment Interest Rate						2.00%
Years after cessation of plant operations						10 years
Estimated annual after tax return on nuclear decommissioning funds	4.80%					4.80%
Exelon Generation Co L L C [Member] \| Maximum [Member]
Asset Retirement Obligations [Line Items]
Investment Interest Rate						3.00%
Years after cessation of plant operations						70 years
Estimated annual after tax return on nuclear decommissioning funds	6.40%					6.40%
Nuclear Plant [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)				$ 138,000,000		$ 928,000,000	436,000,000
Asset Retirement Obligation, Revision of Estimate	$ 178,000,000
Nuclear decommissioning
Asset Retirement Obligations [Line Items]
Proceeds from Customers		$ 4,000,000				24,000,000
Nuclear decommissioning \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)						34,000,000	$ 61,000,000
Asset Retirement Obligation, Revision of Estimate						444,000,000
Zion Station [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Decommissioning Liability, Noncurrent	$ 114,000,000					$ 114,000,000