Supplemental Financial Information - Summary of Taxes other than Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Financial Information Tables [Line Items]
Utility Taxes	[1]	$ 474	$ 456	$ 449
Property		407	396	302
Payroll		201	200	159
Other		118	102	185
Total taxes other than income		1,200	1,154	1,095
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes	[1]	105	89	79
Property		250	240	205
Payroll		118	118	89
Other		16	18	16
Total taxes other than income		489	465	389
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes	[1]	236	238	241
Property		27	25	24
Payroll		28	28	27
Other		5	2	7
Total taxes other than income		296	293	299
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes	[1]	133	128	129
Property		11	15	14
Payroll		14	14	13
Other		2	2	2
Total taxes other than income		160	159	158
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Utility Taxes	[1]	85	86	82
Property		119	114	112
Payroll		16	18	15
Other		4	3	4
Total taxes other than income		$ 224	$ 221	$ 213

[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. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.