Commitments and Contingencies, Long-Term Power Sales Contracts, Litigation (Details) (USD $) In Billions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Commitments and Contingencies, Long-Term Power Sales Contracts, Litigation
Total commitments for purchase obligation	$ 8.4
Baltimore Gas and Electric Company | From October 2011 to May 2012
Long Term Purchase Commitment
Residential and small commercial electricity requirements, percent covered by purchase commitments (as a percent)	100.00%
Baltimore Gas and Electric Company | From June 2012 to September 2012
Long Term Purchase Commitment
Residential and small commercial electricity requirements, percent covered by purchase commitments (as a percent)	75.00%
Baltimore Gas and Electric Company | From October 2012 to May 2013
Long Term Purchase Commitment
Residential and small commercial electricity requirements, percent covered by purchase commitments (as a percent)	50.00%
Baltimore Gas and Electric Company | From June 2013 to September 2013
Long Term Purchase Commitment
Residential and small commercial electricity requirements, percent covered by purchase commitments (as a percent)	25.00%