Debt and Credit Agreements - Commercial Paper Borrowings Outstanding (Details) - USD ($)		Dec. 31, 2016	Sep. 30, 2016	May 26, 2016		Dec. 31, 2015	Dec. 31, 2014	Aug. 10, 2013	Aug. 01, 2011
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount	[1]	$ 1,510,000,000
Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	9,450,000,000				$ 10,375,000,000
Outstanding commercial paper		$ 688,000,000				$ 1,162,000,000
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 600,000,000	[4]			$ 500,000,000
Exelon Corporate [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		1.12%				0.88%	0.53%
Letters of Credit Outstanding, Amount	[1]	$ 29,000,000
Exelon Corporate [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 500,000,000
Outstanding commercial paper		$ 0				0
Average Interest Rate on Commercial Paper Borrowings		0.70%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		1.14%
Letters of Credit Outstanding, Amount		$ 1,170,000,000
Line of Credit Facility, Current Borrowing Capacity		50,000,000
Exelon Generation Co L L C [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	5,300,000,000				5,450,000,000
Outstanding commercial paper		$ 620,000,000				$ 0
Average Interest Rate on Commercial Paper Borrowings		0.94%				0.49%
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 500,000,000				$ 275,000,000
Exelon Generation Co L L C [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		7,000,000
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.89%	0.50%
Letters of Credit Outstanding, Amount	[1]	2,000,000
Line of Credit Facility, Current Borrowing Capacity		34,000,000
Commonwealth Edison Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 1,000,000,000
Outstanding commercial paper		$ 0				$ 294,000,000
Average Interest Rate on Commercial Paper Borrowings		0.77%				0.53%
Commonwealth Edison Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 12,000,000
PECO Energy Co [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount	[1]	2,000,000
Line of Credit Facility, Current Borrowing Capacity		34,000,000
PECO Energy Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 600,000,000
Outstanding commercial paper		0				$ 0
PECO Energy Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 21,000,000
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.95%				0.87%	0.61%
Letters of Credit Outstanding, Amount	[1]	$ 0
Line of Credit Facility, Current Borrowing Capacity		5,000,000
Baltimore Gas and Electric Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	600,000,000				$ 600,000,000
Outstanding commercial paper		$ 45,000,000				$ 210,000,000
Average Interest Rate on Commercial Paper Borrowings		0.77%				0.48%
Baltimore Gas and Electric Company [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 2,000,000
Pepco Energy Services [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						1.22%	0.78%
Pepco Holdings LLC [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	0				$ 875,000,000
Outstanding commercial paper		$ 0				$ 484,000,000
Average Interest Rate on Commercial Paper Borrowings		1.03%				0.80%
Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 900,000,000					$ 1,500,000,000
Line of Credit Facility, Current Borrowing Capacity			$ 900,000,000
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.90%				0.68%	0.46%
Letters of Credit Outstanding, Amount	[1]	$ 0
Potomac Electric Power Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	500,000,000				$ 500,000,000
Outstanding commercial paper		$ 23,000,000				$ 64,000,000
Average Interest Rate on Commercial Paper Borrowings		0.71%				0.44%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.79%	0.42%
Letters of Credit Outstanding, Amount	[1]	$ 0
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Delmarva Power and Light Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	500,000,000				$ 500,000,000
Outstanding commercial paper		$ 0				$ 105,000,000
Average Interest Rate on Commercial Paper Borrowings		0.68%				0.47%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.65%	0.52%
Letters of Credit Outstanding, Amount	[1]	$ 1,000,000
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Atlantic City Electric Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	350,000,000				$ 350,000,000
Outstanding commercial paper		$ 0				$ 5,000,000
Average Interest Rate on Commercial Paper Borrowings		0.65%				0.46%

[1] Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.

[2] Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015, respectively

[3] Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million, $5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

[4] Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.