Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Depreciation and amortization	$ 564	$ 543
Operating and maintenance	1,858	1,764
Capital expenditures	1,217	1,447
Income Tax Expense (Benefit)	(54)	56
Interest Expense	217	617
Total interest expense to affiliates, net	10	6
Scenario Adjustment [Member]
Purchased power and fuel from affiliate	318
Exelon Generation Co L L C [Member]
Depreciation and amortization	211	214
Operating and maintenance	938	965
Capital expenditures	535	841
Income Tax Expense (Benefit)	(199)	(1)
Interest Expense	73	65
Purchased power and fuel from affiliate	349	321
Total interest expense to affiliates, net	12	17
Exelon Generation Co L L C [Member] | Scenario Adjustment [Member]
Purchased power and fuel from affiliate	321
Total interest expense to affiliates, net	17
Commonwealth Edison Co [Member]
Depreciation and amortization	173	167
Operating and maintenance	287	292
Capital expenditures	341	346
Income Tax Expense (Benefit)	65	(58)
Interest Expense	77	350
Total interest expense to affiliates, net	3	3
PECO Energy Co [Member]
Depreciation and amortization	58	57
Operating and maintenance	256	164
Capital expenditures	184	122
Income Tax Expense (Benefit)	34	55
Interest Expense	25	26
Total interest expense to affiliates, net	3	3
Baltimore Gas and Electric Company [Member]
Depreciation and amortization	108	93
Operating and maintenance	163	124
Capital expenditures	146	134
Income Tax Expense (Benefit)	58	55
Interest Expense	23	29
Total interest expense to affiliates, net	4	4
Baltimore Gas and Electric Company [Member] | Scenario Adjustment [Member]
Total interest expense to affiliates, net	$ 4