Commitments and Contingencies, Long-Term Power Sales Contracts, Litigation (Details) (USD $) In Billions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2011 Baltimore Gas and Electric Company July 1, 2011 to May 2012	Jun. 30, 2011 Baltimore Gas and Electric Company From June 2012 to September 2012	Jun. 30, 2011 Baltimore Gas and Electric Company From October 2012 to May 2013	Jun. 30, 2011 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)		100.00%	75.00%	50.00%	25.00%
Total commitments for purchase obligation	$ 7