Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($)
Derivative [Line Items]
Cash Collateral Held	$ 163
Letters of credit held	60
Fair Value, Concentration of Risk, Maximum Amount of Loss
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	1,065
Fair Value, Concentration of Risk, Maximum Amount of Loss \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	111
Fair Value, Concentration of Risk, Maximum Amount of Loss \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	226
Fair Value, Concentration of Risk, Maximum Amount of Loss \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	715
Fair Value, Concentration of Risk, Maximum Amount of Loss \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	13
Credit Collateral [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	223
Credit Collateral [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	0
Credit Collateral [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	47
Credit Collateral [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	176
Credit Collateral [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	0
Net Exposure [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	842
Net Exposure [Member] \| Financial institutions
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	32
Net Exposure [Member] \| Investor-owned utilities, marketers, power producers
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	711
Net Exposure [Member] \| Energy cooperatives and municipalities
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	62
Net Exposure [Member] \| Other [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	37
Net Exposure [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	111
Net Exposure [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	179
Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	539
Net Exposure [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 13
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Number of Counterparties	1
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| Internal Investment Grade
Derivative [Line Items]
Number of Counterparties	0
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Number of Counterparties	0
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Number of Counterparties	1
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Number of Counterparties	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 106
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| Internal Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| Internal Noninvestment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	106
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member] \| External Credit Rating, Non Investment Grade
Derivative [Line Items]
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 0

Letters of credit held related to credit risk

No definition available.

Name:	exc_LettersOfCreditHeld
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents number of counterparties with a concentrated credit risk greater than 10% of net exposure.

+ References

No definition available.

+ Details

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- Definition

Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.1)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.(a),2)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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- Definition

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13537-108611

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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

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