Preferred Securities (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Class of Stock [Line Items]
Shares outstanding	1,900,000
Dollar amount	$ 190.00
Temporary Equity [Line Items]
Shares outstanding	874,720		874,720
Dollar amount	87.00		87.00
Preferred Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	100,000,000		100,000,000
Series A Preferred Stock [Member]
Temporary Equity [Line Items]
Shares outstanding	300,000		300,000
Dollar amount	30.00		30.00
Redemption price	$ 106.000
Dividend rate per dollar amount	$ 3.80
Series B Preferred Stock [Member]
Temporary Equity [Line Items]
Shares outstanding	150,000		150,000
Dollar amount	15.00		15.00
Redemption price	$ 102.000
Dividend rate per dollar amount	$ 4.30
Series C Preferred Stock [Member]
Temporary Equity [Line Items]
Shares outstanding	274,720		274,720
Dollar amount	27.00		27.00
Redemption price	$ 112.500
Dividend rate per dollar amount	$ 4.40
Series D Preferred Stock [Member]
Temporary Equity [Line Items]
Shares outstanding	150,000		150,000
Dollar amount	15.00		15.00
Redemption price	$ 104.000
Dividend rate per dollar amount	$ 4.68
Series 6.97% Preferred Stock [Member]
Class of Stock [Line Items]
Shares outstanding	500,000
Dollar amount	50.00
Redemption price	$ 100.350	[1]
Dividend Rate Percentage	6.97%
Series 6.7% Preferred Stock [Member]
Class of Stock [Line Items]
Shares outstanding	400,000
Dollar amount	40.00
Redemption price	$ 100.670	[1]
Dividend Rate Percentage	6.70%
Series 6.99% Preferred Stock [Member]
Class of Stock [Line Items]
Shares outstanding	600,000
Dollar amount	60.00
Redemption price	$ 101.050	[1]
Dividend Rate Percentage	6.99%
Series 7.125% Preferred Stock [Member]
Class of Stock [Line Items]
Shares outstanding	400,000
Dollar amount	40.00
Redemption price	$ 100.360	[1]
Dividend Rate Percentage	7.125%
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]
Temporary Equity [Line Items]
Dollar amount	$ 87.00		$ 87.00
PECO Energy Co [Member] | Cumulative Preferred Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	15,000,000		15,000,000
Baltimore Gas and Electric Company [Member] | Preference Stock [Member]
Preferred Securities Additional Narrative Information [Line Items]
Shares authorized	6,500,000
Preferred Stock, Par or Stated Value Per Share	$ 100.000

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