Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Depreciation and amortization	$ 2,153	$ 1,881	$ 1,347
Operating and maintenance	7,270	7,961	5,184
Capital expenditures	5,395	5,789	4,042
Income Tax Expense (Benefit)	1,044	627	1,457
Interest Expense	1,315	891	701
Exelon Generation Co L L C [Member]
Depreciation and amortization	856	768	570
Operating and maintenance	3,960	4,398	2,827
Capital expenditures	2,752	3,554	2,491
Income Tax Expense (Benefit)	615	500	1,056
Interest Expense	298	226	170
Commonwealth Edison Co [Member]
Depreciation and amortization	669	610	554
Operating and maintenance	1,211	1,182	1,031
Capital expenditures	1,433	1,246	1,028
Income Tax Expense (Benefit)	152	239	250
Interest Expense	566	294	330
PECO Energy Co [Member]
Depreciation and amortization	228	217	202
Operating and maintenance	647	698	698
Capital expenditures	537	422	481
Income Tax Expense (Benefit)	162	127	146
Interest Expense	103	111	122
Baltimore Gas and Electric Company [Member]
Depreciation and amortization	348	298	274
Operating and maintenance	551	622	530
Capital expenditures	587	582	592
Income Tax Expense (Benefit)	134	7	75
Interest Expense	106	128	113
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member]
Operating and maintenance	3
Interest Expense	5
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member] | Regulatory Assets [Member]
Depreciation and amortization	2
Income Tax Expense (Benefit)	4
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member] | Other Postretirement Benefits [Member]
Income Tax Expense (Benefit)	$ 4