Supplemental Financial Information - Summary of Taxes other than Income (Details) (USD $) In Millions, unless otherwise specified	10 Months Ended		12 Months Ended
	Dec. 31, 2012		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Supplemental Financial Information Tables [Line Items]
Utility Taxes			$ 456	[1]	$ 449	[1]	$ 463	[1]
Property			396		302		227
Payroll			200		159		131
Other			102		185		198
Total taxes other than income			1,154		1,095		1,019
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes			89	[1]	79	[1]	82	[1]
Property			240		205		189
Payroll			118		89		78
Other			18		16		20
Total taxes other than income			465		389		369
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes			238	[1]	241	[1]	239	[1]
Property			25		24		22
Payroll			28		27		26
Other			2		7		8
Total taxes other than income			293		299		295
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes			128	[1]	129	[1]	141	[1]
Property			15		14		13
Payroll			14		13		12
Other			2		2		(4)
Total taxes other than income			159		158		162
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes	59	[1]	86	[1]	82	[1]	75	[1]
Property			114		112		111
Payroll			18		15		18
Other			3		4		4
Total taxes other than income			$ 221		$ 213		$ 208

[1] Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s and BGE’s utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues, respectively. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.