Debt and Credit Agreements - Narrative (Details) - Derivative Contract [Domain] $ in Millions					3 Months Ended	6 Months Ended
		Jul. 06, 2015 USD ($)	Jun. 11, 2014 USD ($)	Jun. 01, 2014 shares	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	May. 01, 2014 USD ($)
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 1,708	$ 1,191
Line of Credit Facility, Maximum Borrowing Capacity	[1]				$ 8,500	8,500
Bridge Loan								$ 7,200
equity units issued | shares				23,000,000
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions					$ 35
Subordinated Borrowing, Interest Rate					2.50%
Long-term Debt					$ 131	$ 131
Parent Company [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.28%	0.28%
Basis Points For Libor Based Borrowings					0.0128	0.0128
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 260	617
Basis points adders for prime-based borrowings					0.08%	0.08%
Basis Points For Libor Based Borrowings					0.0108	0.0108
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 39	538
Basis points adders for prime-based borrowings					0.28%	0.28%
Basis Points For Libor Based Borrowings					0.0019	0.0019
Debt Instrument, Face Amount							3,200
PECO Energy Co [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.00%	0.00%
Basis Points For Libor Based Borrowings					0.009	0.009
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 37	35
Basis points adders for prime-based borrowings					0.00%	0.00%
Basis Points For Libor Based Borrowings					0.01	0.01
Revolving Credit Facility [Member] | Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]				$ 1,000	$ 1,000
Revolving Credit Facility [Member] | PECO Energy Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]				600	600
Revolving Credit Facility [Member] | Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]				600	600
Parent [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]				500	500
AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt							$ 1
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum							2.33%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum							3.55%
Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[3]				750	750
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					4,200	$ 4,200
Convertible Debt Securities [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Subordinated Long-term Debt					$ 1,110
Maximum [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.07%	0.07%
Basis Points For Libor Based Borrowings					0.0017	0.0017
ExGen425Feb062021 [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate							4.44%
Debt Instrument, Face Amount							$ 300
AGE143Nov172017 [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate					1.43%	1.43%
Debt Instrument, Face Amount					$ 50	$ 50
TaxExemptBonds255 [Member] | First Mortgage Bonds [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.50%
Debt Instrument, Face Amount	[4]				435	$ 435
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						2.70%
AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.29%
Debt Instrument, Face Amount					$ 39	$ 39
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						2.96%
AVSR [Member] | AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						3.56%
SeniorSecuredNotes525January152014Member [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt							$ 500
Interest Rate							5.35%
SeniorSecuredNotes525January152014Member [Member] | Junior Subordinated Debt [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 1,150
Subsequent Event [Member] | AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		3.55%

[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 expire on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 30, 2015, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million, $16 million, $21 million and $1 million, respectively.

[2] Syndicated revolvers include credit facility commitments of $22 million, $27 million and $27 million for Exelon Corporate, PECO and BGE, respectively, which expire in August 2018.

[3] In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination.

[4] The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.