Shareholder Equity Preferred and Preference Securities (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 190	$ 190
Preferred Stock, Shares Outstanding	1,900,000	1,900,000
Preferred Stock, Shares Authorized	6,500,000
Preference Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share		$ 100
Preferred Stock, Shares Authorized		6,500,000
Series 6.97% Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	6.97%
Series 6.97% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 50	$ 50
Preferred Stock, Redemption Price Per Share	$ 100.00
Preferred Stock, Shares Outstanding	500,000	500,000
Series 6.7% Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	6.70%
Series 6.7% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 40	$ 40
Preferred Stock, Redemption Price Per Share	$ 100.00
Preferred Stock, Shares Outstanding	400,000	400,000
Series 6.99% Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	6.99%
Series 6.99% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 60	$ 60
Preferred Stock, Redemption Price Per Share	$ 100.00
Preferred Stock, Shares Outstanding	600,000	600,000
Series 7.125% Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage	7.125%
Series 7.125% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 40
Preferred Stock, Redemption Price Per Share	$ 100.00
Preferred Stock, Shares Outstanding	400,000	400,000
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	100,000,000	100,000,000
Preferred Stock [Member] | Commonwealth Edison Co [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	850,000	850,000
Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share	$ 100
Cumulative Preferred Stock [Member] | Commonwealth Edison Co [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Authorized		6,810,451