The amount remitted to variable interest entities for rate stabilization bonds.

Name:	ceg_AmountRemittedToVariableInterestEntitiesOnRateStabilizationBonds
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of variable interest entities consolidated in the reporting entity's consolidated financial statements.

+ Details

Name:	ceg_NumberOfVariableInterestEntities
Namespace Prefix:	ceg
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

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

- Definition

Percentage of ownership interest in certain nonconsolidated VIEs where none of the equity holders consolidate these VIEs.

+ Details

Name:	ceg_OwnershipPercentageOfNonconsolidatedVariableInterestEntities
Namespace Prefix:	ceg
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ Details

Name:	ceg_VariableInterestEntityConsolidatedCarryingAmountAssets
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ceg_VariableInterestEntityConsolidatedCarryingAmountAssetsAndLiabilitiesAbstract
Namespace Prefix:	ceg
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the consolidated Variable Interest Entity's current assets included in the reporting entity's statement of financial position.

+ Details

Name:	ceg_VariableInterestEntityConsolidatedCarryingAmountAssetsCurrent
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's noncurrent assets included in the reporting entity's statement of financial position.

+ Details

Name:	ceg_VariableInterestEntityConsolidatedCarryingAmountAssetsNoncurrent
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ Details

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

- Definition

The carrying amount of the consolidated Variable Interest Entity's current portion of liabilities included in the reporting entity's statement of financial position.

+ Details

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

- Definition

The carrying amount of the consolidated Variable Interest Entity's noncurrent portion of liabilities included in the reporting entity's statement of financial position.

+ Details

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

- Definition

This item represents the amount of financial or other support the reporting entity has provided (explicitly or implicitly) to the Variable Interest Entity (VIE) that it was not previously contractually required to provide or that the reporting entity intends to provide, including, for example, situations in which the reporting entity assisted the VIE in obtaining another type of support.

+ Details

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

- 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.

+ Details

Name:	us-gaap_VariableInterestEntityLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2011 Consolidated Variable Interest Entities	Dec. 31, 2010 Consolidated Variable Interest Entities	Jun. 30, 2011 RSB BondCo. LLC	Jun. 30, 2010 RSB BondCo. LLC	Jun. 30, 2011 RSB BondCo. LLC	Jun. 30, 2010 RSB BondCo. LLC	Jun. 30, 2011 Unconsolidated Variable Interest Entities	Dec. 31, 2010 Unconsolidated Variable Interest Entities	Jun. 30, 2011 Retail gas supply contract Parental guarantee
Variable Interest Entity
Number of consolidated variable interest entities	4
Number of Variable Interest Entities not consolidated by equity holders							6	6
Ownership percentage, nonconsolidated variable interest entity (in percentage)	100.00%
Remittance by BGE of payments received from customers for rate stabilization			$ 15.9	$ 18.2	$ 38.5	$ 42.0
Obligations under gas supply agreement									75
Carrying amount of consolidated assets and liabilities of VIE
Current assets	455.4	516.6
Noncurrent assets	50.9	57.7
Total Assets	506.3	574.3
Current liabilities	282.8	345.5
Noncurrent liabilities	376.3	399.0
Total Liabilities	$ 659.1	$ 744.5