Financing Activities (Details) (USD $)	6 Months Ended				6 Months Ended							6 Months Ended					1 Months Ended				1 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009	Jun. 30, 2011 Constellation Energy;	Jun. 30, 2011 Constellation Energy; Syndicated Revolver October 2013	Jun. 30, 2011 Constellation Energy; Commodity-linked August 2014	Jun. 30, 2011 Constellation Energy; Bilateral September 2014	Jun. 30, 2011 Constellation Energy; Bilateral December 2014	Jun. 30, 2011 Constellation Energy; Bilateral June 2014	Jun. 30, 2011 Constellation Energy; Bilateral September 2013	Jun. 30, 2011 Baltimore Gas and Electric Company	Jul. 31, 2011 Baltimore Gas and Electric Company	Dec. 31, 2010 Baltimore Gas and Electric Company	Jun. 30, 2010 Baltimore Gas and Electric Company	Dec. 31, 2009 Baltimore Gas and Electric Company	Jul. 31, 2011 Subsidiary of Constellation Energy	Jul. 31, 2011 Subsidiary of Constellation Energy Project financing MW	Jun. 30, 2011 Revolving credit facility expiring in 2015	Jul. 31, 2011 Amended and extended existing reserve based lending facility	Jan. 31, 2011 7.00% Fixed-Rate Notes, due April 1, 2012	Jan. 31, 2011 5.15% Fixed-Rate Notes, due December 1, 2020
Credit facilities
Bank lines of credit under committed credit facilities					$ 4,200,000,000	$ 2,500,000,000	$ 500,000,000	$ 550,000,000	$ 250,000,000	$ 250,000,000	$ 150,000,000						$ 150,000,000	$ 40,000,000	$ 600,000,000	$ 150,000,000
Letters of credit issued including the commodities linked credit facility					1,400,000,000
Letters of credit issued					1,100,000,000		300,000,000
Line of credit facility adjusted borrowing capacity							300,000,000
Term of senior secured credit facility (in years)																	3
Maximum amount upto which amount committed under senior credit facility may be increased																	200,000,000			500,000,000
Amount borrowed under line of credit facility																	130,000,000			74,000,000
Commercial paper outstanding	20,600,000	32,400,000			20,600,000								30,000,000
Commercial paper weighted average interest rate (as a percent)					6.54%
Solar facility (MW)																		30
Term of variable rate note for solar facility (in years)	19
Notional amount of interest rate swaps																	30,000,000
Bridge loan																	26,000,000
Equity bridge loan																	28,000,000
Debt
Retirement of aggregate principal amount of fixed term notes																					213,500,000
Long-term debt																						550,000,000
Loss on redemption of 7.00% fixed-rate notes due April 1, 2012, pre-tax																					5,000,000
Interest rate (as a percent)																					7.00%	5.15%
Net available liquidity
Credit facilities					3,700,000,000		300,000,000					600,000,000
Less: Letters of credit issued					(1,100,000,000)		(300,000,000)
Undrawn facilities					2,600,000,000							600,000,000
Net available facilities					2,600,000,000							600,000,000
Add: Cash and cash equivalents					800,000,000							100,000,000
Less: Reserved cash					(200,000,000)
Net available liquidity					3,200,000,000							700,000,000
Cash and cash equivalents	$ 954,800,000	$ 2,028,500,000	$ 1,603,200,000	$ 3,440,000,000								$ 120,600,000		$ 50,000,000	$ 260,200,000	$ 13,600,000
Credit Facility Compliance and Covenants
Credit facilities, required debt-capitalization ratio percentage (as a percent)					65.00%							65.00%
Credit facilities, calculated debt-capitalization ratio percentage (as a percent)					33.00%							43.00%