Preferred and Preference Securities - Summary of Preference Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Class of Stock [Line Items]
Shares outstanding	1,900,000		1,900,000
Dollar amount	$ 190		$ 190
Series 7.125% Preferred Stock [Member]
Class of Stock [Line Items]
Dividend rate percentage	7.125%
Redemption price	$ 100	[1]
Shares outstanding	400,000		400,000
Dollar amount	40		40
Series 6.97% Preferred Stock [Member]
Class of Stock [Line Items]
Dividend rate percentage	6.97%
Redemption price	$ 100	[1]
Shares outstanding	500,000		500,000
Dollar amount	50		50
Series 6.7% Preferred Stock [Member]
Class of Stock [Line Items]
Dividend rate percentage	6.70%
Redemption price	$ 100	[1]
Shares outstanding	400,000		400,000
Dollar amount	40		40
Series 6.99% Preferred Stock [Member]
Class of Stock [Line Items]
Dividend rate percentage	6.99%
Redemption price	$ 100	[1]
Shares outstanding	600,000		600,000
Dollar amount	$ 60		$ 60

[1] Redeemable, at the option of BGE, at the indicated dollar amounts per share, plus accrued and unpaid dividends.