Taxes Other Than Income Taxes (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 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	$ 36.4	$ 31.6	$ 106.6	$ 93.1
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	$ 20.2	$ 20.4	$ 62.8	$ 61.6