Taxes Other Than Income Taxes (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Taxes Other than Income Taxes
Gross receipts taxes and other surcharges and fees accounted for on a gross basis and included in revenues	$ 35.5	$ 30.5	$ 70.2	$ 61.5
Baltimore Gas and Electric Company
Taxes Other than Income Taxes
Gross receipts taxes and other surcharges and fees accounted for on a gross basis and included in revenues	$ 19.6	$ 19.3	$ 42.6	$ 41.2

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