Debt and Credit Agreements - Commercial Paper Borrowings Outstanding (Details) - USD ($)		Dec. 31, 2015		Dec. 31, 2014	May. 30, 2014		Mar. 28, 2014	[1],[2]	Dec. 31, 2013
Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]	$ 8,150,000,000		$ 8,300,000,000
Outstanding commercial paper		504,000,000		$ 424,000,000
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size	[3]	$ 8,425,000,000
Exelon Corporate [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.88%		0.53%					0.35%
Exelon Corporate [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]			$ 500,000,000
Outstanding commercial paper		$ 0		0
Exelon Corporate [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size		500,000,000	[3]		$ 500,000,000	[1],[2]
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Bilateral letters of credit		275,000,000		200,000,000
Exelon Generation Co L L C [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]	5,450,000,000		5,600,000,000
Outstanding commercial paper		$ 0		$ 0
Average Interest Rate on Commercial Paper Borrowings		0.49%		0.32%
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size	[3]	$ 5,725,000,000
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.89%		0.50%					0.37%
Commonwealth Edison Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]			$ 1,000,000,000
Outstanding commercial paper		$ 294,000,000		$ 304,000,000
Average Interest Rate on Commercial Paper Borrowings		0.53%		0.33%
Commonwealth Edison Co [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size		$ 1,000,000,000	[3]				$ 1,000,000,000
PECO Energy Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]			$ 600,000,000
Outstanding commercial paper		0		$ 0
PECO Energy Co [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size		$ 600,000,000	[3]		600,000,000	[1],[2]
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.87%		0.61%					0.31%
Baltimore Gas and Electric Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[1],[2]			$ 600,000,000	$ 600,000,000
Outstanding commercial paper		$ 210,000,000		$ 120,000,000
Average Interest Rate on Commercial Paper Borrowings		0.48%		0.29%
Baltimore Gas and Electric Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size	[3]	$ 600,000,000

[1] Excludes additional credit facilities for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. The agreements for these facilities expired on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of December 31, 2015, letters of credit issued under these facilities totaled $7 million, $14 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

[2] Reflects aggregate bank commitments under the revolving and bilateral credit agreements (with the exception of $275 million and $200 million bilateral agreements for Generation as of December 31, 2015 and 2014, respectively) that backstop the commercial paper program. See discussion and Credit Facilities table below for items affecting effective program size.

[3] Excludes additional credit facilities for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. The agreements for these facilities expired on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of December 31, 2015, letters of credit issued under these facilities totaled $7 million, $14 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.