Debt and Credit Agreements - Summary of Bank Commitments, Credit Facility Borrowings and Available Capacity (Details) (USD $)	Dec. 31, 2014		May 30, 2014		Mar. 28, 2014
Short-term Debt [Line Items]
Facility draws	$ 0
Outstanding letters of credit	1,190,000,000	[1]
Actual available capacity	7,310,000,000
To Support Additional Commercial Paper	6,771,000,000	[2]
Exelon Corporate [Member]
Short-term Debt [Line Items]
Facility draws	0
Outstanding letters of credit	6,000,000	[1]
Actual available capacity	494,000,000
To Support Additional Commercial Paper	494,000,000	[2]
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Facility draws	0
Outstanding letters of credit	1,181,000,000	[1]
Actual available capacity	4,619,000,000
To Support Additional Commercial Paper	4,504,000,000	[2]
Credit facility agreements with minority and community banks	50,000,000
Letters of credit	9,000,000
Bilateral letters of credit	200,000,000
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Facility draws	0
Outstanding letters of credit	2,000,000	[1]
Actual available capacity	998,000,000
To Support Additional Commercial Paper	694,000,000	[2]
Credit facility agreements with minority and community banks	34,000,000
Letters of credit	16,000,000
PECO Energy Co [Member]
Short-term Debt [Line Items]
Facility draws	0
Outstanding letters of credit	1,000,000	[1]
Actual available capacity	599,000,000
To Support Additional Commercial Paper	599,000,000	[2]
Credit facility agreements with minority and community banks	34,000,000
Letters of credit	21,000,000
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Facility draws	0
Outstanding letters of credit	0	[1]
Actual available capacity	600,000,000
To Support Additional Commercial Paper	480,000,000	[2]
Credit facility agreements with minority and community banks	5,000,000
Letters of credit	1,000,000
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size	8,500,000,000	[3]
Revolving Credit Facility [Member] | Exelon Corporate [Member]
Short-term Debt [Line Items]
Maximum Program Size	500,000,000	[3]	500,000,000	[4],[5]
Revolving Credit Facility [Member] | Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Maximum Program Size	5,800,000,000	[3]	5,300,000,000.0	[5]
Revolving Credit Facility [Member] | Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Maximum Program Size	1,000,000,000	[3]			1,000,000,000	[4],[5]
Revolving Credit Facility [Member] | PECO Energy Co [Member]
Short-term Debt [Line Items]
Maximum Program Size	600,000,000	[3]	600,000,000	[4],[5]
Revolving Credit Facility [Member] | Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Maximum Program Size	$ 600,000,000	[3]

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

[2] Excludes $200 million bilateral credit facilities that do not back Generation’s commercial paper program.

[3] Excludes additional credit facility agreements 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. These facilities expired on October 17, 2014 and were renewed at the same amount through October 16, 2015. These facilities are solely utilized to issue letters of credit. As of December 31, 2014, letters of credit issued under these agreements totaled $9 million, $16 million, $21 million and $1 million for Generation, ComEd, PECO and BGE, respectively. Also, excludes the unsecured bridge credit facility of $3.2 billion at December 31, 2014, to support the PHI transaction discussed below

[4] Excludes additional credit facility agreements 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. These facilities expired on October 17, 2014 and were renewed at the same amount through October 16, 2015. These facilities are solely utilized to issue letters of credit. As of December 31, 2014, letters of credit issued under these agreements totaled $9 million, $16 million, $21 million and $1 million for Generation, ComEd, PECO and BGE, respectively. Also, excludes the unsecured bridge credit facility of $3.2 billion at December 31, 2014, to support the PHI transaction discussed below.

[5] aggregate bank commitments under the revolving and bilateral credit agreements (with the exception of $200 million bilateral agreements for Generation) that backstop the commercial paper program. See discussion below and Credit Agreements table below for items affecting effective program size.