Debt and Credit Agreements - Lines of Credit under Committed Credit Facilities (Details) (USD $)	Sep. 30, 2014		Jun. 30, 2014	Jun. 11, 2014		May 01, 2014
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 8,500,000,000	[1]
Bridge Loan			3,900,000,000	3,900,000,000		7,200,000,000
Line of Credit Facility, Current Borrowing Capacity	22,000,000
Parent [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500,000,000	[1],[2]
Exelon Generation Co L L C [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	50,000,000
Outstanding letters of credit	9,000,000
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5,300,000,000
Exelon Generation Co L L C [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Outstanding letters of credit	300,000,000	[1],[2]		100,000,000	[1],[2]
Exelon Generation Co L L C [Member] | Letter of Credit [Member] | Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Outstanding letters of credit	100,000,000	[1],[2]
Commonwealth Edison Co [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	34,000,000
Outstanding letters of credit	18,000,000
Commonwealth Edison Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,000,000,000	[1],[2]
PECO Energy Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	27,000,000
PECO Energy Co [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	34,000,000
Outstanding letters of credit	21,000,000
PECO Energy Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600,000,000	[1],[2]
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	27,000,000
Baltimore Gas and Electric Company [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5,000,000
Outstanding letters of credit	1,000,000
Baltimore Gas and Electric Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600,000,000	[1],[2]
Syndicated Revolver 1 [Member] | Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5,100,000,000	[1],[2]
Syndicated Revolver 2 [Member] | Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200,000,000	[1],[2]

[1] 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 September 30, 2014, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $9 million, $18 million, $21 million and $1 million, respectively. Also, excludes the unsecured bridge credit facility of $3.9 billion to support the PHI transaction discussed below, as well as, applicable asset divestitures.

[2] Includes credit facilities for Exelon Corporate, PECO and BGE with aggregate commitments of $22 million, $27 million and $27 million, respectively, that expire in August 2018.