Consolidated Statement of Changes in Shareholders Equity (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Income taxes	$ 646
Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	(154)
Exelon Generation Co L L C [Member]
Income taxes	290
Exelon Generation Co L L C [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Income taxes	53
PECO Energy Co [Member]
Income taxes	82
Commonwealth Edison Co [Member]
Income taxes	221
Baltimore Gas and Electric Company [Member]
Income taxes	103
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