Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($)
WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150
Corporate [Member] \| SoftAgree362Dec2025 \| Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest Rate	3.62%
Debt Instrument, Face Amount	$ 4
Exelon Generation Co L L C [Member] \| WestMedMarch2026 \| Non-Recourse Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR + 3
Debt Instrument, Face Amount	$ 150
Exelon Generation Co L L C [Member] \| EEPF253April2021 \| Notes Payable, Other Payables[Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
Debt Instrument, Face Amount	$ 1
Exelon Generation Co L L C [Member] \| EEPF4242021 \| Notes Payable, Other Payables[Member]
Debt Instrument [Line Items]
Interest Rate	4.24%
Debt Instrument, Face Amount	$ 1
Commonwealth Edison Co [Member] \| FMB313Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.13%
Debt Instrument, Face Amount	$ 700
Commonwealth Edison Co [Member] \| FMB300March2050 [Member] \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.75%
Debt Instrument, Face Amount	$ 450
PECO Energy Co [Member] \| FMB305Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.05%
Debt Instrument, Face Amount	$ 375
PECO Energy Co [Member] \| FMB285Sep2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.85%
Debt Instrument, Face Amount	$ 375
Baltimore Gas and Electric Company [Member] \| SN225June2031
Debt Instrument [Line Items]
Interest Rate	2.25%
Debt Instrument, Face Amount	$ 600
Potomac Electric Power Company [Member] \| FMB232Mar2031 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.32%
Debt Instrument, Face Amount	$ 150
Potomac Electric Power Company [Member] \| FMB329Sep2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.29%
Debt Instrument, Face Amount	$ 125
Delmarva Power and Light Company [Member] \| FMB324Mar2051 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.24%
Debt Instrument, Face Amount	$ 125
Atlantic City Electric Company [Member] \| FMB230Mar2031 \| First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.30%
Debt Instrument, Face Amount	$ 350

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69C
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 55
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

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.

+ Details

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