Capitalization (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended										1 Months Ended
	Nov. 30, 2009	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Nov. 30, 2009 7.00% Fixed-Rate Notes, due April 1, 2012	Dec. 31, 2010 7.00% Fixed-Rate Notes, due April 1, 2012	Dec. 31, 2009 7.00% Fixed-Rate Notes, due April 1, 2012	Dec. 31, 2011 6.20% deferrable interest subordinated debentures due October 15, 2043 to wholly owned BGE Capital Trust II relating to trust preferred securities	Dec. 31, 2010 6.20% deferrable interest subordinated debentures due October 15, 2043 to wholly owned BGE Capital Trust II relating to trust preferred securities	Dec. 31, 2011 Rate Stabilization Bonds	Dec. 31, 2010 Rate Stabilization Bonds	Dec. 31, 2011 Constellation Energy;	Dec. 31, 2010 Constellation Energy;	Dec. 31, 2011 Constellation Energy; 8.625% Series A Junior Subordinated Debentures, due June 15, 2063	Dec. 31, 2010 Constellation Energy; 8.625% Series A Junior Subordinated Debentures, due June 15, 2063	Jan. 31, 2011 Constellation Energy; 7.00% Fixed-Rate Notes, due April 1, 2012	Dec. 31, 2010 Constellation Energy; 7.00% Fixed-Rate Notes, due April 1, 2012	Dec. 31, 2011 Constellation Energy; 4.55% Fixed-Rate Notes, due June 15, 2015	Dec. 31, 2010 Constellation Energy; 4.55% Fixed-Rate Notes, due June 15, 2015	Dec. 31, 2011 Constellation Energy; 5.15% Fixed-Rate Notes, due December 1, 2020	Dec. 31, 2010 Constellation Energy; 5.15% Fixed-Rate Notes, due December 1, 2020	Dec. 31, 2011 Constellation Energy; 7.60% Fixed-Rate Notes, due April 1, 2032	Dec. 31, 2010 Constellation Energy; 7.60% Fixed-Rate Notes, due April 1, 2032	Dec. 31, 2011 Nonregulated businesses	Dec. 31, 2010 Nonregulated businesses	Dec. 31, 2011 Nonregulated businesses 4.10% Pollution control loan, due July 1, 2014	Dec. 31, 2010 Nonregulated businesses 4.10% Pollution control loan, due July 1, 2014	Dec. 31, 2011 Nonregulated businesses Tax-exempt variable rate notes, due April 1, 2024	Dec. 31, 2010 Nonregulated businesses Tax-exempt variable rate notes, due April 1, 2024	Dec. 31, 2011 Nonregulated businesses 7.3% Fixed Rate Note, due June 1, 2012	Dec. 31, 2010 Nonregulated businesses 7.3% Fixed Rate Note, due June 1, 2012	Dec. 31, 2011 Nonregulated businesses Upstream Gas Property asset-based lending agreement due July 16, 2016	Dec. 31, 2010 Nonregulated businesses Upstream Gas Property asset-based lending agreement due July 16, 2016	Dec. 31, 2011 Nonregulated businesses Sacramento Solar Project Financing Agreement due December 31, 2030	Dec. 31, 2011 Nonregulated businesses Denver International Airport Solar Loan Agreement due June 30, 2031	Dec. 31, 2011 Nonregulated businesses Holyoke Solar, LLC Loan Agreement due December 31, 2031	Dec. 31, 2011 Nonregulated businesses Secured Solar Credit Lending Agreement due July 7, 2014	Dec. 31, 2011 Baltimore Gas and Electric Company	Dec. 31, 2010 Baltimore Gas and Electric Company	Dec. 31, 2011 Baltimore Gas and Electric Company Other long term debt	Dec. 31, 2010 Baltimore Gas and Electric Company Other long term debt	Dec. 31, 2011 Baltimore Gas and Electric Company 3.50% Notes, due November 15, 2021	Nov. 30, 2011 Baltimore Gas and Electric Company 3.50% Notes, due November 15, 2021	Dec. 31, 2011 Baltimore Gas and Electric Company 6.125% Notes, due July 1, 2013	Dec. 31, 2010 Baltimore Gas and Electric Company 6.125% Notes, due July 1, 2013	Dec. 31, 2011 Baltimore Gas and Electric Company 5.90% Notes, due October 1, 2016	Dec. 31, 2010 Baltimore Gas and Electric Company 5.90% Notes, due October 1, 2016	Dec. 31, 2011 Baltimore Gas and Electric Company 5.20% Notes, due June 15, 2033	Dec. 31, 2010 Baltimore Gas and Electric Company 5.20% Notes, due June 15, 2033	Dec. 31, 2011 Baltimore Gas and Electric Company 6.35% Notes, due October 1, 2036	Dec. 31, 2010 Baltimore Gas and Electric Company 6.35% Notes, due October 1, 2036	Dec. 31, 2011 Baltimore Gas and Electric Company Medium-term notes, Series E	Dec. 31, 2010 Baltimore Gas and Electric Company Medium-term notes, Series E
Debt
Long-term debt			$ 5,024.8							$ 394.6	$ 454.4	$ 2,294.1	$ 2,499.7	$ 450.0	$ 450.0		$ 213.5	$ 550.0	$ 550.0	$ 550.0	$ 550.0	$ 700.0	$ 700.0	$ 368.8	$ 114.7	$ 20.0	$ 20.0	$ 75.0	$ 75.0	$ 1.6	$ 1.7	$ 83.0	$ 18.0	$ 40.7	$ 7.5	$ 11.0	$ 130.0	$ 2,361.9		$ 1,709.6	$ 1,431.5	$ 300.0		$ 400.0	$ 400.0	$ 300.0	$ 300.0	$ 200.0	$ 200.0	$ 400.0	$ 400.0	$ 109.6	$ 131.5
Bank lines of credit under committed credit facilities			130.0									4,200.0
Fair Value of Interest Rate Swaps												44.1	36.2
Deferrable interest subordinated debentures			257.7	257.7				257.7	257.7																													257.7	257.7
Interest rate (as a percent)		3.50%						6.20%	6.20%					8.625%	8.625%		7.00%	4.55%	4.55%	5.15%	5.15%	7.60%	7.60%			4.10%	4.10%			7.30%	7.30%											3.50%	3.50%	6.125%	6.125%	5.90%	5.90%	5.20%	5.20%	6.35%	6.35%
Loss on redemption of Zero Coupon Senior Notes, pre-tax	(16.0)	(16.0)			(16.0)	(51.6)	(16.0)									(5.0)
Unamortized discount and premium			(5.1)	(3.9)
Current portion of long-term debt			(174.9)	(305.3)
Total long-term debt			$ 4,844.8	$ 4,448.8