This element represents the total investments in variable interest entities as of the balance sheet date.

No definition available.

Name:	ceg_InvestmentsInVariableInterestEntities
Namespace Prefix:	ceg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of variable interest entities (VIEs) not consolidated.

+ References

No definition available.

+ Details

Name:	ceg_NumberOfVariableInterestEntitiesNotConsolidated
Namespace Prefix:	ceg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The carrying value of other ownership interests as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	ceg_OtherOwnershipInterests
Namespace Prefix:	ceg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ceg_PowerContractMonetizationVIEsAbstract
Namespace Prefix:	ceg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents power sales contracts assumed from a counterparty with previously existing VIEs, number.

+ References

No definition available.

+ Details

Name:	ceg_PowerSalesContractsAssumedWithVIENumber
Namespace Prefix:	ceg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the entity's maximum exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

No definition available.

+ Details

Name:	ceg_VariableInterestEntityMaximumLossExposureAmount
Namespace Prefix:	ceg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ceg_VariableInterestEntityNonconsolidatedCarryingAmountAssetsLiabilitiesAndOtherInformationAbstract
Namespace Prefix:	ceg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph a

-URI http://asc.fasb.org/extlink&oid=6970148&loc=d3e5728-111685

+ Details

Name:	us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE).

+ References

+ Details

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

Investments (Details 6) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Mar. 31, 2005 contract	Dec. 31, 2011	Dec. 31, 2010
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Total assets		$ 696.1	$ 781.2
Total liabilities		410.3	495.8
Ownership interest		53.5	48.7
Other ownership interests		232.3	236.7
Power contract Monetization VIEs
Number of power sales contracts assumed with previously existing VIEs	2
Letters of credit
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		15.5	24.9
Carrying amounts of investments
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		39.8	41.4
Debt and payment guarantees
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		5.0	5.0
Unconsolidated Variable Interest Entities.
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Number of Variable Interest Entities not consolidated by equity holders		6	6
Power contract monetization entities
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Total assets		386.5	492.9
Total liabilities		303.9	382.6
Other ownership interests		82.6	110.3
Power contract monetization entities \| Letters of credit
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		15.5	24.9
All Other VIEs
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Total assets		309.6	288.3
Total liabilities		106.4	113.2
Ownership interest		53.5	48.7
Other ownership interests		149.7	126.4
All Other VIEs \| Carrying amounts of investments
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		39.8	41.4
All Other VIEs \| Debt and payment guarantees
Carrying amount of nonconsolidated assets, liabilities and other information of VIE
Our maximum exposure to loss		$ 5.0	$ 5.0