The minimum amount of commitments, following completion of the pending merger, the merged entity must expend to satisfy the terms of disclosed arrangements in which the entity must commit resources to supply goods or services to one or more customers.

Name:	ceg_PendingMergerCommitmentsMadeByMergedEntityMinimum
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The conversion ratio of common stock to be used in the pending merger.

+ Details

Name:	ceg_PendingMergerCommonStockConversionRatio
Namespace Prefix:	ceg
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents details pertaining to pre-tax costs related to pending merger.

+ Details

Name:	ceg_PendingMergerCostsPretax
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of distribution rate given to each residential customer on completion of pending merger.

+ Details

Name:	ceg_PendingMergerProposedDistributionRateCreditPerResidentialCustomer
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the amount of a termination fee that may be payable upon exercising the right to terminate a pending merger.

+ Details

Name:	ceg_PendingMergerTerminationFeePayable
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ceg_ScheduleOfPendingMergerLineItems
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Pending Merger with Exelon Corporation (Details) (USD $)	1 Months Ended	3 Months Ended	9 Months Ended
	Apr. 30, 2011	Sep. 30, 2011	Sep. 30, 2011	Apr. 28, 2011
Combined entity
Pending merger with Exelon Corporation
Proposed amount of distribution rate credit for residential customers (per customer)				$ 100
Commitments made by combined entity				250,000,000
Constellation Energy.
Pending merger with Exelon Corporation
Number of common shares of Constellation Energy to be cancelled and converted into the right to receive for each share of Exelon (in shares)	0.93
Termination fee payable under specified circumstances				200,000,000
Pre-tax costs related to our pending merger		8,300,000	40,100,000
Exelon Corporation
Pending merger with Exelon Corporation
Termination fee payable under specified circumstances				$ 800,000,000