Consolidated Statement of Changes in Shareholders Equity (Unaudited) (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Income taxes	$ 184
Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	(154)
Exelon Generation Co L L C [Member]
Income taxes	151
Exelon Generation Co L L C [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	53
Atlantic City Electric Company [Member]
Income taxes	(33)
PECO Energy Co [Member]
Income taxes	43
Commonwealth Edison Co [Member]
Income taxes	77
Baltimore Gas and Electric Company [Member]
Income taxes	66
Potomac Electric Power Company [Member]
Income taxes	(25)
Constellation Energy Group LLC [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	77
Constellation Energy Group LLC [Member] | Exelon Generation Co L L C [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	$ 77