Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
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- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

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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.

+ References

No definition available.

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any 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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- 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))
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Period Type:	instant

- Definition

Amount of borrowings from a bank classified as other, maturing within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Debt and Credit Agreements - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018	Oct. 16, 2018
Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
Debt Instrument, Interest Rate Terms	LIBOR plus 1%
Exelon Generation Co L L C [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 30
Line of Credit Facility, Maximum Borrowing Capacity	95
Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
Debt Instrument, Interest Rate Terms	LIBOR plus 1%
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 125
Debt Instrument, Interest Rate Terms	LIBOR plus 0.55%
FMB400Oct2028 [Member] \| Atlantic City Electric Company [Member] \| First Mortgage [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 350
Interest Rate			4.00%
FMB775Nov2018 [Member] \| Atlantic City Electric Company [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate	7.75%
FMB431Nov2048 [Member] \| Potomac Electric Power Company [Member] \| First Mortgage [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 100
Interest Rate		4.31%