Identifies the line item(s) where the income (loss) on related party agreements is reported in the statement of income or other statement of financial performance.

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

- Definition

Represents the percentage of request for borrowings submitted to entity.

+ Details

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

- Definition

Represents the percentage of request for borrowings submitted to entity's subsidiaries.

+ Details

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

- Definition

Represents terms of agreements with related parties (in years).

+ Details

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

- Definition

This element represents the percentage of nuclear output to be purchased by third party.

+ Details

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

- Definition

This element represents the percentage of nuclear output to be purchased.

+ Details

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

- Definition

Approximate average annual revenue to be recognized for service agreement with related party.

+ Details

Name:	ceg_RelatedPartyTransactionAverageExpectedAnnualRevenueFromServicesAgreement
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents corporate function costs that were directly charged or allocated to a subsidiary based on a total percentage of expected use during the period.

+ Details

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

- Definition

Expected revenue to be recognized for service agreement with related party in the next year.

+ Details

Name:	ceg_RelatedPartyTransactionExpectedRevenueFromServicesAgreementNextYear
Namespace Prefix:	ceg
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the high end of the range of the required purchases of power from a related party, that is not sold to third parties, over the specified term of a power purchase agreement, percent.

+ Details

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

- Definition

Represents the low end of the range of the required purchases of power from a related party, that is not sold to third parties, over the specified term of a power purchase agreement, percent.

+ Details

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

- Definition

The amount of purchased power from a related party charged against earnings for the period.

+ Details

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

- Definition

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ Details

Name:	us-gaap_DerivativeBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The reference rate for the variable rate of the interest rate derivative, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ Details

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

- Definition

Gain or loss on entity's disposition of equity in securities of subsidiaries or 50 percent or less owned persons. Reflects the difference in the parent company's carrying amount of the equity interest in the subsidiary (or equity method investee) immediately before and after all stock transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 13
-Subparagraph g
-Article 9

+ Details

Name:	us-gaap_GainLossOnSaleOfStockInSubsidiaryOrEquityMethodInvestee
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount borrowed under the credit facility as of the balance-sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityAmountOutstanding
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph k
-Subparagraph 1
-Article 4

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
-Paragraph 2
-Subparagraph d

+ Details

Name:	us-gaap_RelatedPartyTransactionDueFromToRelatedParty
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenues, net of returns and allowances, realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
-Paragraph 2
-Subparagraph c

+ Details

Name:	us-gaap_RelatedPartyTransactionRevenuesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended			6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2011 CENG	Jun. 30, 2011 CENG	Jun. 30, 2011 CENG Power purchase agreement (PPA)	Jun. 30, 2010 CENG Power purchase agreement (PPA)	Jun. 30, 2011 CENG Power purchase agreement (PPA)	Jun. 30, 2010 CENG Power purchase agreement (PPA)	Dec. 31, 2010 CENG Power purchase agreement (PPA)	Jun. 30, 2011 CENG Power services agency agreement (PSA)	Jun. 30, 2010 CENG Power services agency agreement (PSA)	Jun. 30, 2011 CENG Power services agency agreement (PSA)	Jun. 30, 2010 CENG Power services agency agreement (PSA)	Jun. 30, 2011 CENG Administrative services agreement (ASA)	Jun. 30, 2010 CENG Administrative services agreement (ASA)	Jun. 30, 2011 CENG Administrative services agreement (ASA)	Jun. 30, 2010 CENG Administrative services agreement (ASA)	Dec. 31, 2010 CENG Administrative services agreement (ASA)	May 31, 2011 CENG Revolving promissory note	Jun. 30, 2011 Baltimore Gas and Electric Company	Jun. 30, 2010 Baltimore Gas and Electric Company	Jun. 30, 2011 Baltimore Gas and Electric Company	Jun. 30, 2010 Baltimore Gas and Electric Company	May 31, 2011 EDF Revolving promissory note	May 31, 2011 Constellation Energy. Revolving promissory note
Related Party Transactions:
The low end of the range of the required purchases of power from CENG's nuclear plants not sold to third parties (as a percent)					85.00%
The high end of the range of the required purchases of power from CENG's nuclear plants not sold to third parties (as a percent)					90.00%
Purchase of nuclear output of CENG (as a percent)				50.01%
Purchase of nuclear output by EDF (as a percent)				49.99%
Average expected annual revenue from agreement with CENG										$ 16
Expected 2011 revenue from agreement with CENG														48
Increase (Decrease) in Earnings					(209.3)	(222.1)	(404.1)	(420.6)		4.0	4.0	8.0	8.0	12.0	16.5	24.0	33.0
Income Statement Classification							Fuel and purchased energy expenses					Nonregulated revenues				Operating expenses
Amount receivable from (payable to) related to agreements with CENG					(46.5)		(46.5)		(47.6)					4.0		4.0		5.5
Maximum borrowing capacity																			62.5
Percentage of request for borrowings submitted to entity (as a percent)																									50.00%
Percentage of request for borrowings submitted to entity's subsidiaries (as a percent)																								50.00%
Variable rate offered by prime banks																			rate at which deposits of United States dollars are offered by prime banks in the London interbank market
Spread on variable rate offered by prime banks (as a percent)																			2.50%
Outstanding borrowings																			15.0
Gain on U.S. Department of Energy Settlement	35.5	35.5	35.5
Electricity purchased for resale expenses																				73.2	114.6	129.9	238.6
Corporate function costs directly assigned or allocated to BGE																				$ 44.3	$ 42.3	$ 91.8	$ 78.5
Term of agreement with CENG (in years)										5		5