Debt and Credit Agreements - Narrative (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended																					3 Months Ended			0 Months Ended	3 Months Ended	0 Months Ended	3 Months Ended											0 Months Ended
	Jun. 01, 2014	Jun. 30, 2014	Sep. 30, 2014		Sep. 30, 2014		Jun. 11, 2014	May 01, 2014	Jun. 05, 2013	Sep. 30, 2014 Parent Company [Member]	Sep. 30, 2014 Commonwealth Edison Co [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Sep. 18, 2014 ExGen Texas Power, LLC [Member]	Sep. 30, 2014 PECO Energy Co [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]	Mar. 28, 2014 Standby Letters of Credit [Member] Commonwealth Edison Co [Member]	Sep. 30, 2014 Revolving Credit Facility [Member] Commonwealth Edison Co [Member]		Sep. 30, 2014 Revolving Credit Facility [Member] Exelon Generation Co L L C [Member]	Sep. 30, 2014 Revolving Credit Facility [Member] PECO Energy Co [Member]		Sep. 30, 2014 Revolving Credit Facility [Member] Baltimore Gas and Electric Company [Member]		Sep. 30, 2014 Parent [Member] Revolving Credit Facility [Member]		Sep. 30, 2014 Convertible Debt Securities [Member]	Jun. 30, 2014 Convertible Debt Securities [Member]	Jun. 11, 2014 Convertible Debt Securities [Member]	Apr. 01, 2014 Maximum [Member]	Sep. 30, 2014 Maximum [Member]	Apr. 01, 2014 Minimum [Member]	Sep. 30, 2014 Minimum [Member]	Sep. 18, 2014 Senior Notes [Member] Secured Debt [Member] ExGen Texas Power, LLC [Member]	Feb. 06, 2014 Senior Notes [Member] Secured Debt [Member] ExGen Renewables I, LLC [Member]	Sep. 30, 2014 Long Term Debt Issuances [Member]	Sep. 30, 2014 Long Term Debt Issuances [Member] ExgenRenewablesI425June62021[Member] Unsecured Debt [Member] Exelon Generation Co L L C [Member]	Sep. 18, 2014 Long Term Debt Issuances [Member] ExgenRenewablesI425June62021[Member] Non Recourse Debt [Member] Exelon Generation Co L L C [Member]	Feb. 06, 2014 Long Term Debt Issuances [Member] ExgenRenewablesI425June62021[Member] Non Recourse Debt [Member] Exelon Generation Co L L C [Member]	Feb. 06, 2014 Long Term Debt Issuances [Member] ExgenRenewablesI425June62021[Member] Minimum [Member] Non Recourse Debt [Member] Exelon Generation Co L L C [Member]	Feb. 06, 2014 Interest Rate Swap [Member] Exelon Generation Co L L C [Member]	Sep. 18, 2014 Interest Rate Swap [Member] ExGen Texas Power, LLC [Member]	Oct. 24, 2014 Subsequent Event [Member] Exelon Generation Co L L C [Member]	Oct. 06, 2014 Subsequent Event [Member] Senior Loans [Member] Exelon Generation Co L L C [Member]	Oct. 01, 2014 Subsequent Event [Member] Senior Loans [Member] PECO Energy Co [Member]	Oct. 01, 2014 Subsequent Event [Member] Senior Loans [Member] PECO Energy Co [Member]	Oct. 06, 2014 Subsequent Event [Member] Maximum [Member] Senior Loans [Member] Exelon Generation Co L L C [Member]	Oct. 06, 2014 Subsequent Event [Member] Minimum [Member] Senior Loans [Member] Exelon Generation Co L L C [Member]	Mar. 28, 2014 Revolving Credit Facility [Member] Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount Of Aggregate Letters of Credit Available																$ 500,000,000
Line of Credit Facility, Expiration Date					Mar. 28, 2019
Additional Amount of Aggregate Letters of Credit Available																500,000,000
Outstanding borrowings/facility draws																																										100,000,000
Line of Credit Facility, Maximum Borrowing Capacity			8,500,000,000	[1]	8,500,000,000	[1]							20,000,000				1,000,000,000	[1],[2]	5,300,000,000	600,000,000	[1],[2]	600,000,000	[1],[2]	500,000,000	[1],[2]																							1,000,000,000
Cumulative amount in commitments																								315,000,000	[1],[2]
Basis points adders for prime-based borrowings										0.275%	0.075%	0.275%		0.00%	0.00%															0.065%
Basis Points For Libor Based Borrowings										0.01275	0.01075	0.01275		0.009	0.01															0.00165
Bridge Loan		3,900,000,000					3,900,000,000	7,200,000,000
Interest Expense, Commercial Paper			11,000,000		20,000,000
Subordinated Debt, Amount																										1,150,000,000
equity units issued	23,000,000
Shares Issued, Price Per Share									$ 35																		$ 50.00
Proceeds from Issuance of Subordinated Long-term Debt																										1,110,000,000
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions		60,000,000	35,000,000
Subordinated Borrowing, Interest Rate			2.50%
Equity Units, Annual Distribution Rate					6.50%
Forward Contract Payment Rate			4.00%
Per Unit Conversion Rate For Equity Security Units																										$ 50
Market Price required for Equity Unit Conversion			$ 43.7484
Common Shares Issueable At Maturity																														1.1429		1.4286
Equity Units Share Price																													$ 43.7484		$ 35
Share Price			$ 35		$ 35
Long-term Debt			131,000,000		131,000,000																							1,150,000,000					675,000,000	300,000,000		300,000,000
Debt Instrument, Collateral Amount			2,700,000,000		2,700,000,000
Interest Rate																																			2.50%		4750000.00%	4.25%	1.00%	2.03%	2.34%				5.00%	3.143%	3.056%
Derivative, Notional Amount																																								240,000,000	505,000,000
Repayments of First Mortgage Bond																																												250,000,000
Repayments of Secured Debt																																											$ 11,000,000

[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.