Debt and Credit Agreements (Details) (USD $)	6 Months Ended																	6 Months Ended																																	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Syndicated Revolver [Member]	Jun. 30, 2013 Exelon Corporate [Member]	Jun. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Medium Term Notes, 7.3% June 1,2012 [Member]	Jun. 30, 2012 Exelon Corporate [Member] Long Term Debt Retirements [Member] Senior Notes [Member] Senior Notes, 7.6% Due 2032 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Jan. 23, 2013 Exelon Generation Co L L C [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Commercial Paper [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Syndicated Revolver [Member]		Jun. 30, 2013 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]	Jan. 23, 2013 Exelon Generation Co L L C [Member] Bilateral Credit Facility [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] Senior Notes, 4.25% June 15, 2022 [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Fixed Rate Debt [Member] Senior Notes, 5.6% June 15, 2042 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Senior Notes [Member] Senior Notes, 4.25% June 15, 2022 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] DOE Financing Project [Member] DOE Project Financing, 3.092% January 2, 2037 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Issuances [Member] Energy Efficiency Project Financing [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] First Mortgage Bond Series 98, 7.6% April 1, 2032 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Armstrong Co Tax Exempt, 5% December 1,2042 [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Upstream Gas Property [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Clean Horizons [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Capital Lease Obligations [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] Kennett Square Capital Lease, 7.83%, September 20, 2020 [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Suboridanted Debentures [Member]		Jun. 30, 2013 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Solar Revolver [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member] Long Term Debt Retirements [Member] Solar Revolver [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Commercial Paper [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Syndicated Revolver [Member]		Jun. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] First Mortgage Bonds 7.500% July1,2013 [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Long Term Debt Retirements [Member] First Mortgage Bonds [Member] Fixed Rate Debt [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member] Syndicated Revolver [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Syndicated Revolver [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Issuances [Member] Senior Notes [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Rate Stabilization Bonds, April 1, 2017 [Member]	Jun. 30, 2012 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Medium Term, Notes 6.73% 6.75% June 15, 2012 [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Long Term Debt Retirements [Member] Senior Notes [Member] Senior Notes 6.125% July1,2013 [Member]
Credit Agreements [Abstract]
Additional amounts available upon request under current credit facilities																																$ 500,000,000
Basis points adders for prime-based borrowings	0.0065			0.275			0.275																									0.275												0.075
Basis points adders for LIBOR-based borrowings	0.0165			1.275			1.275																									1.275								1.000				1.075
Bilateral letters of credit								75,000,000
Amount Of Aggregate Letters of Credit Available																																500,000,000
Accounts Receivable Agreement [Abstract]
Short-term notes payable - accounts receivable agreement	210,000,000	210,000,000																																						210,000,000	210,000,000
Gross accounts receivable pledged as collateral	286,000,000	289,000,000																																						286,000,000	289,000,000
AVSR Project Development Debt Agreement [Abstract]
DOE interest rate swap	485,000,000
Long-Term Debt [Abstract]
Long-term debt to affiliate							1,534,000,000		2,007,000,000
Long-term debt	16,121,000,000	17,190,000,000			2,000,000	441,000,000	4,975,000,000		5,245,000,000						523,000,000	787,000,000			69,000,000	9,000,000	450,000,000	1,000,000	46,000,000	3,000,000	1,000,000	1,000,000		450,000,000	[1]	6,000,000	6,000,000	4,707,000,000	5,315,000,000					127,000,000	125,000,000	1,648,000,000	1,647,000,000			1,746,000,000	1,446,000,000			300,000,000	33,000,000	31,000,000	110,000,000	400,000,000
Long-term debt to financing trusts	648,000,000	648,000,000																														206,000,000	206,000,000							184,000,000	184,000,000			258,000,000	258,000,000
Interest rate on long-term debt					7.30%	7.60%									4.25%	5.60%	2.21%		3.092%	4.40%	6.15%	7.83%	5.00%	2.27%	2.563%		7.83%	8.625%	[1]	1.95%	2.49%						7.625%	7.50%										3.35%	5.72%	5.68%		6.125%
Minimum interest rate on long-term debt																		2.535%																																	6.73%
Maximum interest rate on long-term debt																		2.922%																																	6.75%
Long Term Debt																	3,000,000	197,000,000
Line Of Credit Facility [Abstract]
Aggregate bank commitments under unsecured revolving credit facilities	8,400,000,000		500,000,000								5,300,000,000	[2]	300,000,000	100,000,000																					1,000,000,000	[2]						600,000,000	[2]			600,000,000	[2]
Footnotes To Line Of Credit Facility [Abstract]
Credit facility agreements with minority and community banks							50,000,000																									34,000,000								34,000,000				5,000,000
Letters of credit							24,000,000																									26,000,000								21,000,000				1,000,000
Short Term Debt [Line Items]
Commercial paper borrowings										$ 276,000,000																								$ 374,000,000

[1] Represents debt obligations assumed by Exelon as part of the merger on March 12, 2012 that became callable at face value on June 15, 2013. Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable as of December 31, 2012 included in long-term debt to affiliate on Generation’s Consolidated Balance Sheets and notes receivable from affiliates at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets. The third-party debt obligations were reported in Long-term Debt on Exelon’s Consolidated Balance Sheets as of December 31, 2012. The debentures were redeemed and the intercompany loan agreements repaid on June 15, 2013.

[2] 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 18, 2013 and are solely utilized to issue letters of credit. As of June 30, 2013, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $24 million, $26 million, $21 million and $1 million, respectively.