Preferred and Preference Securities (Details) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	May 01, 2013
Preferred Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	100,000,000	100,000,000
Commonwealth Edison Co [Member] | Preferred Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	850,000	850,000
Commonwealth Edison Co [Member] | Cumulative Preferred Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	6,810,451	6,810,451
PECO Energy Co [Member]
Preferred Securities Additional Narrative Information [Line Items]
Preferred securities			$ 87
Baltimore Gas and Electric Company [Member] | Preference Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	6,500,000	6,500,000
Preferred stock, par value	100	100