Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) $ in Millions	3 Months Ended
Mar. 31, 2026 USD ($) counterparty
Derivative [Line Items]
Cash collateral	$ 36
Letters of credit held	86
Total Exposure Before Credit Collateral
Derivative [Line Items]
Maximum exposure	2,535
Total Exposure Before Credit Collateral \| Internally rated — investment grade
Derivative [Line Items]
Maximum exposure	151
Total Exposure Before Credit Collateral \| Internally rated — non-investment grade
Derivative [Line Items]
Maximum exposure	319
Total Exposure Before Credit Collateral \| Investment grade
Derivative [Line Items]
Maximum exposure	1,979
Total Exposure Before Credit Collateral \| Non-investment grade
Derivative [Line Items]
Maximum exposure	86
Credit Collateral
Derivative [Line Items]
Maximum exposure	122
Credit Collateral \| Internally rated — investment grade
Derivative [Line Items]
Maximum exposure	5
Credit Collateral \| Internally rated — non-investment grade
Derivative [Line Items]
Maximum exposure	58
Credit Collateral \| Investment grade
Derivative [Line Items]
Maximum exposure	41
Credit Collateral \| Non-investment grade
Derivative [Line Items]
Maximum exposure	18
Net Exposure
Derivative [Line Items]
Maximum exposure	2,413
Net Exposure \| Investor-owned utilities, marketers, power producers
Derivative [Line Items]
Maximum exposure	1,218
Net Exposure \| Financial Institutions
Derivative [Line Items]
Maximum exposure	599
Net Exposure \| Energy cooperatives and municipalities
Derivative [Line Items]
Maximum exposure	223
Net Exposure \| Other
Derivative [Line Items]
Maximum exposure	373
Net Exposure \| Internally rated — investment grade
Derivative [Line Items]
Maximum exposure	146
Net Exposure \| Internally rated — non-investment grade
Derivative [Line Items]
Maximum exposure	261
Net Exposure \| Investment grade
Derivative [Line Items]
Maximum exposure	1,938
Net Exposure \| Non-investment grade
Derivative [Line Items]
Maximum exposure	$ 68
Number of Counterparties Greater than 10% of Net Exposure
Derivative [Line Items]
Number of counterparties \| counterparty	1
Number of Counterparties Greater than 10% of Net Exposure \| Internally rated — investment grade
Derivative [Line Items]
Number of counterparties \| counterparty	0
Number of Counterparties Greater than 10% of Net Exposure \| Internally rated — non-investment grade
Derivative [Line Items]
Number of counterparties \| counterparty	0
Number of Counterparties Greater than 10% of Net Exposure \| Investment grade
Derivative [Line Items]
Number of counterparties \| counterparty	1
Number of Counterparties Greater than 10% of Net Exposure \| Non-investment grade
Derivative [Line Items]
Number of counterparties \| counterparty	0
Net Exposure of Counterparties Greater than 10% of Net Exposure
Derivative [Line Items]
Maximum exposure	$ 457
Net Exposure of Counterparties Greater than 10% of Net Exposure \| Internally rated — investment grade
Derivative [Line Items]
Maximum exposure	0
Net Exposure of Counterparties Greater than 10% of Net Exposure \| Internally rated — non-investment grade
Derivative [Line Items]
Maximum exposure	0
Net Exposure of Counterparties Greater than 10% of Net Exposure \| Investment grade
Derivative [Line Items]
Maximum exposure	457
Net Exposure of Counterparties Greater than 10% of Net Exposure \| Non-investment grade
Derivative [Line Items]
Maximum exposure	$ 0

Letters of credit held related to credit risk

No definition available.

Name:	ceg_LettersOfCreditHeld
Namespace Prefix:	ceg_
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
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

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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://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-21

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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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

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