Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013		May 15, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in CENG (as a percent)							67.00%
Related Party Income Statement Activity [Abstract]
Operating revenues from affiliates	$ 0	$ 0
Purchased power from affiliate	66	287	400		605
Total interest expense to affiliates, net	10	6	20		13
Total income (loss) in equity method investments	0	(21)	(20)		(30)
Dividends paid on common stock			(533)		(716)
Related Party Balance Sheet [Abstract]
Investments in affiliates	22		22					22
Total payables to affiliates (current)	38		38					116
Equity Method Investment Summarized Financial Information[Abstract]
Purchase of nuclear output by EDF (as a percent)			49.99%
Amortization of energy contract assets and liabilities			113	[1]	306	[1]
Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in CENG (as a percent)	50.01%		50.01%
Total equity investment earnings (losses) - CENG	19	19
Basis difference in investment in CENG	204		204
Related Party Income Statement Activity [Abstract]
Operating revenues from affiliates	201	352	535		744
Operating and maintenance from affiliate	158	148	305		295
Total interest expense to affiliates, net	(12)	(16)	(25)		(34)
Total income (loss) in equity method investments	(1)	(21)	(20)		(30)
Cash distribution paid to member			235		474
Contributions from member			0		0
Related Party Balance Sheet [Abstract]
Mark-to-market derivative assets with affiliates	0		0					0
Total receivables from affiliates (current)	67		67					108
Mark-to-market derivative assets with affiliate (noncurrent assets)	0		0					0
Investments in affiliates	0		0					0
Total payables to affiliates (current)	108		108					181
Total payables to affiliates (noncurrent)	2,917		2,917					2,740
Equity Method Investment Summarized Financial Information[Abstract]
Purchase of nuclear output by EDF (as a percent)			49.99%
Amortization of energy contract assets and liabilities			118	[1]	344	[1]
Exelon Generation Co L L C [Member] | Minimum [Member]
Equity Method Investment Summarized Financial Information[Abstract]
Required purchases of power from CENG's nuclear plants not sold to third parties (as a percent)			85.00%
Commonwealth Edison Co [Member]
Related Party Income Statement Activity [Abstract]
Operating revenues from affiliates	0	0	1		1
Purchased power from affiliate	65	121	173		266
Operating and maintenance from affiliate	39	40	78		76
Total interest expense to affiliates, net	4	4	7		7
Dividends paid on common stock			(153)		(110)
Contributions from parent			112		0
Related Party Balance Sheet [Abstract]
Total receivable from affiliates (noncurrent)	2,606		2,606					2,469
Investments in affiliates	6		6					6
Total payables to affiliates (current)	37		37					83
Mark-to-market derivative liabilities with affiliate (current liabilities)	0		0					0
PECO Energy Co [Member]
Related Party Income Statement Activity [Abstract]
Operating revenues from affiliates	0	0	1		0
Purchased power from affiliate	48	97	135		238
Operating and maintenance from affiliate	24	26	48		50
Total interest expense to affiliates, net	3	3	6		6
Dividends paid on common stock			(160)		(166)
Related Party Balance Sheet [Abstract]
Total receivable from affiliates (noncurrent)	490		490					447
Investments in affiliates	8		8					8
Total payables to affiliates (current)	37		37					58
Baltimore Gas and Electric Company [Member]
Related Party Income Statement Activity [Abstract]
Operating revenues from affiliates	2	4	18		8
Operating and maintenance from affiliate	25	21	50		37
Total interest expense to affiliates, net	(4)	(4)	(8)		(8)
Dividends paid on common stock			0		0
Contributions from parent			0		0
Related Party Balance Sheet [Abstract]
Investments in affiliates	8		8					8
Total payables to affiliates (current)	$ 55		$ 55					$ 55

[1] Included in purchased power and fuel expense on the Registrants' Consolidated Statements of Operations and Comprehensive Income