Retirement Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan Effect Of One Percentage Point Change In Assumed Health Care Cost Trend Rates [Abstract]
Effect of a one percentage point increase in assumed healthcare cost trend on 2010 total service and interest cost components	$ 90,000,000
Effect of a one percentage point increase in assumed healthcare cost trend on postretirement benefit obligation at December 31, 2010	858,000,000
Effect of a one percentage point decrease in assumed healthcare cost trend on 2010 total service and interest cost components	(62,000,000)
Effect of a one percentage point decrease in assumed healthcare cost trend on postretirement benefit obligation at December 31, 2010	(607,000,000)
Prescription Drug Benefit Effect Of Subsidy On Net Periodic Postretirement Benefit Cost [Abstract]
Amortization of the actuarial experience loss			(17,000,000)		3,000,000
Reduction in current period service cost					9,000,000
Reduction in interest cost on the APBO					16,000,000
Effect of federal subsidy on net periodic postretirement benefit costs under the Prescription Drug Act			(17,000,000)		28,000,000
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	422,000,000		462,000,000		2,360,000,000
Federal subsidy payments received not included in contributions			10,000,000		11,000,000
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	825,000,000		820,000,000		542,000,000
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	85,000,000		67,000,000		78,000,000
Projected Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligation	15,452,000,000		16,800,000,000
Fair value of net plan assets	13,564,000,000		13,357,000,000
Accumulated Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligation	15,452,000,000		16,796,000,000
Accumulated benefit obligation	14,552,000,000		15,657,000,000
Fair value of net plan assets	13,564,000,000		13,353,000,000
Exelon Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Regulatory asset increase (decrease) due to updated valuation adjustment	93,000,000
Aoci Valuation Adjustment	(75,000,000)
Constellation Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Regulatory asset increase (decrease) due to updated valuation adjustment	14,000,000
Aoci Valuation Adjustment	2,000,000
Business Services Company [Member]
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	71,000,000	[1]	99,000,000	[1]	48,000,000	[1]
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	7,000,000		5,000,000		7,000,000
Exelon Generation Co L L C [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	149,000,000		178,000,000		1,070,000,000
Federal subsidy payments received not included in contributions			5,000,000		5,000,000
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	347,000,000		341,000,000		249,000,000
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	40,000,000		30,000,000		40,000,000
Commonwealth Edison Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	122,000,000		138,000,000		977,000,000
Federal subsidy payments received not included in contributions			4,000,000		4,000,000
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	309,000,000		282,000,000		213,000,000
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	22,000,000		19,000,000		22,000,000
PECO Energy Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	31,000,000		45,000,000		137,000,000
Federal subsidy payments received not included in contributions			1,000,000		1,000,000
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	43,000,000		50,000,000		32,000,000
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	8,000,000		7,000,000		9,000,000
Baltimore Gas and Electric Company [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	24,000,000		16,000,000		67,000,000
Federal subsidy payments received not included in contributions			2,000,000		3,000,000
Defined Benefit Plan Expense Included In Capital And Operational And Maintenance Expense [Abstract]
Amount included in capital and operating & maintenance expense	55,000,000	[2],[3]	60,000,000	[2],[3]	51,000,000	[2],[3]
Defined Contribution Plan Contributions By Employer [Abstract]
Savings plan matching contributions	8,000,000		7,000,000		7,000,000
Pension Plans Defined Benefit [Member]
Change in benefit obligation:
Net benefit obligation at beginning of year	16,800,000,000		13,538,000,000
Service cost	317,000,000		280,000,000		212,000,000
Actuarial gain (loss)	(1,363,000,000)		1,520,000,000
Interest cost	650,000,000		698,000,000		649,000,000
Plan amendments	1,000,000
Acquisitions/divestitures			1,880,000,000
Curtailments			(10,000,000)
Settlements	(69,000,000)	[4]	(169,000,000)	[4]
Special termination benefits			15,000,000
Gross benefits paid	(877,000,000)	[5]	(952,000,000)	[5]
Net benefit obligation at end of year	15,459,000,000		16,800,000,000		13,538,000,000
Change in plan assets:
Fair value of net plan assets at beginning of year	13,357,000,000		11,302,000,000
Actual return on plan assets	821,000,000		1,484,000,000
Employer contributions	339,000,000		149,000,000
Gross benefits paid	(877,000,000)	[5]	(952,000,000)	[5]
Acquisitions/divestitures - Plan Assets			1,543,000,000
Settlements	(69,000,000)	[4]	(169,000,000)	[4]
Fair value of net plan assets at end of year	13,571,000,000		13,357,000,000		11,302,000,000
Components of net periodic benefit cost:
Service cost	317,000,000		280,000,000		212,000,000
Interest cost	650,000,000		698,000,000		649,000,000
Settlement charges	(9,000,000)		(31,000,000)
Expected return on assets	(1,015,000,000)		(988,000,000)		(939,000,000)
Contractual termination benefit cost			(14,000,000)	[6]
Net periodic benefit cost	537,000,000		500,000,000		267,000,000
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other current liabilities	12,000,000		15,000,000
Pension obligations	1,876,000,000		3,428,000,000
Unfunded status (net benefit obligation less net plan assets)	1,888,000,000		3,443,000,000
Changes in plan assets and benefit obligations recognized in OCI and regulatory assets:
Actuarial gain (Loss)	1,169,000,000		(1,693,000,000)		(744,000,000)
Amortization of actuarial gain (loss)	(562,000,000)		(450,000,000)		(331,000,000)
Current year prior service cost			1,000,000
Amortization of prior service cost	(14,000,000)		(15,000,000)		(14,000,000)
Curtailments			(10,000,000)
Settlements	(8,000,000)		(31,000,000)
Total recognized in OCI and regulatory assets	(1,753,000,000)	[7]	1,188,000,000	[7]	399,000,000	[7]
Changes in plan assets and benefit obligations recognized in OCI	1,071,000,000		283,000,000		181,000,000
Changes in plan assets and benefit obligations recognized in regulatory assets	682,000,000		904,000,000		218,000,000
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax [Abstract]
Prior service cost (credit)	62,000,000		76,000,000
Actuarial loss	6,192,000,000		7,931,000,000
Total components of periodic benefit cost not yet recognized	6,254,000,000	[8]	8,007,000,000	[8]
Benefits included in accumulated other comprehensive income	3,523,000,000		4,594,000,000
Benefits included in regulatory assets	2,731,000,000		3,413,000,000
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets To Be Amortized Before Tax [Abstract]
Prior service cost (credit)	14,000,000
Actuarial loss	427,000,000
Total components of periodic benefit cost to be amortized	441,000,000	[9]
Benefits included in accumulated other comprehensive income	232,000,000
Benefits included in regulatory assets	209,000,000
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	339,000,000		149,000,000		2,094,000,000	[10]
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan Expected Future Benefit Payments In Year One	929,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Two	851,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Three	873,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Four	902,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Five	1,015,000,000
Defined Benefit Plan Expected Future Benefit Payments In Five Fiscal Years Thereafter	5,257,000,000
Total estimated future benefits payments through 2020	9,827,000,000
Pension Plans Defined Benefit [Member] | Remeasurement [Member]
Design Changes Impact [Abstract]
Discount rate used for remeasurement due to design changes	4.21%
Pension Plans Defined Benefit [Member] | Equity Securities [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	31.00%
Total weighted average asset allocation	35.00%		35.00%
Pension Plans Defined Benefit [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	38.00%
Total weighted average asset allocation	37.00%		40.00%
Pension Plans Defined Benefit [Member] | Alternative Investments [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	31.00%	[11]
Total weighted average asset allocation	28.00%	[11]	25.00%	[11]
Pension Plans Defined Benefit [Member] | Exelon Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Benefit obligation increase (decrease) reflecting actual census data	8,000,000
Pension Plans Defined Benefit [Member] | Constellation Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Benefit obligation increase (decrease) reflecting actual census data	23,000,000
Pension Plans Defined Benefit [Member] | Business Services Company [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	91,000,000		63,000,000		157,000,000	[10]
Pension Plans Defined Benefit [Member] | Exelon Generation Co L L C [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	119,000,000		48,000,000		954,000,000	[10]
Pension Plans Defined Benefit [Member] | Commonwealth Edison Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	118,000,000		25,000,000		873,000,000	[10]
Pension Plans Defined Benefit [Member] | PECO Energy Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	11,000,000		13,000,000		110,000,000	[10]
Pension Plans Defined Benefit [Member] | Baltimore Gas and Electric Company [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions			54,000,000		197,000,000
Other Postretirement Benefit Plans Defined Benefit [Member]
Change in benefit obligation:
Net benefit obligation at beginning of year	4,820,000,000		4,062,000,000
Service cost	162,000,000		156,000,000		142,000,000
Actuarial gain (loss)	(551,000,000)		313,000,000
Interest cost	194,000,000		205,000,000		207,000,000
Plan participants' contributions	34,000,000		34,000,000
Plan amendments	15,000,000		(103,000,000)
Acquisitions/divestitures			362,000,000
Curtailments			(8,000,000)
Special termination benefits			6,000,000
Gross benefits paid	(223,000,000)		(219,000,000)
Federal subsidy on benefits paid			12,000,000
Net benefit obligation at end of year	4,451,000,000		4,820,000,000		4,062,000,000
Reinsurance proceeds received			1.3
Change in plan assets:
Fair value of net plan assets at beginning of year	2,135,000,000		1,797,000,000
Actual return on plan assets	209,000,000		197,000,000
Employer contributions	83,000,000		325,000,000
Plan participants' contributions	34,000,000		34,000,000
Gross benefits paid	(223,000,000)		(219,000,000)
Benefits paid net	(223,000,000)	[5]	(218,000,000)	[5]
Fair value of net plan assets at end of year	2,238,000,000		2,135,000,000		1,797,000,000
Components of net periodic benefit cost:
Service cost	162,000,000		156,000,000		142,000,000
Interest cost	194,000,000		205,000,000		207,000,000
Expected return on assets	(132,000,000)		(115,000,000)		(111,000,000)
Curtailments charges			(7,000,000)
Contractual termination benefit cost			(6,000,000)	[6]
Net periodic benefit cost	288,000,000		320,000,000		275,000,000
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other current liabilities	23,000,000		23,000,000
Non-pension postretirement benefit obligations	2,190,000,000		2,662,000,000
Unfunded status (net benefit obligation less net plan assets)	2,213,000,000		2,685,000,000
Changes in plan assets and benefit obligations recognized in OCI and regulatory assets:
Actuarial gain (Loss)	628,000,000		(304,000,000)		(74,000,000)
Amortization of actuarial gain (loss)	(83,000,000)		(81,000,000)		(66,000,000)
Current year prior service cost	15,000,000		(109,000,000)
Amortization of prior service cost	19,000,000		17,000,000		38,000,000
Current year transition (asset) obligation			1,000,000
Amortization of transition obligation	0		(11,000,000)		(9,000,000)
Curtailments			(1,000,000)
Total recognized in OCI and regulatory assets	(677,000,000)	[7]	120,000,000	[7]	37,000,000	[7]
Changes in plan assets and benefit obligations recognized in OCI	352,000,000		39,000,000		13,000,000
Changes in plan assets and benefit obligations recognized in regulatory assets	325,000,000		81,000,000		24,000,000
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax [Abstract]
Prior service cost (credit)	(73,000,000)		(107,000,000)
Actuarial loss	474,000,000		1,185,000,000
Total components of periodic benefit cost not yet recognized	401,000,000	[8]	1,078,000,000	[8]
Benefits included in accumulated other comprehensive income	161,000,000		514,000,000
Benefits included in regulatory assets	240,000,000		564,000,000
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets To Be Amortized Before Tax [Abstract]
Prior service cost (credit)	(16,000,000)
Actuarial loss	32,000,000
Total components of periodic benefit cost to be amortized	16,000,000	[9]
Benefits included in accumulated other comprehensive income	7,000,000
Benefits included in regulatory assets	9,000,000
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	83,000,000	[12]	323,000,000	[12]	277,000,000	[12]
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan Expected Future Benefit Payments In Year One	204,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Two	210,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Three	219,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Four	228,000,000
Defined Benefit Plan Expected Future Benefit Payments In Year Five	238,000,000
Defined Benefit Plan Expected Future Benefit Payments In Five Fiscal Years Thereafter	1,383,000,000
Total estimated future benefits payments through 2020	2,482,000,000
Disclosure Of Expected Gross Prescription Drug Subsidy Receipts [Abstract]
Prescription Drug Subsidy Receipts Year One	0
Prescription Drug Subsidy Receipts Year Two	0
Prescription Drug Subsidy Receipts Year Three	0
Prescription Drug Subsidy Receipts Year Four	0
Prescription Drug Subsidy Receipts Year Five	0
Prescription Drug Subsidy Receipts Five Fiscal Years Thereafter	0
Other Postretirement Benefit Plans Defined Benefit [Member] | Remeasurement [Member]
Design Changes Impact [Abstract]
Discount rate used for remeasurement due to design changes	4.66%
Other Postretirement Benefit Plans Defined Benefit [Member] | Equity Securities [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	41.00%
Total weighted average asset allocation	45.00%		46.00%
Other Postretirement Benefit Plans Defined Benefit [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	39.00%
Total weighted average asset allocation	37.00%		40.00%
Other Postretirement Benefit Plans Defined Benefit [Member] | Alternative Investments [Member]
Defined Benefit Plan Weighted Average Asset Allocations [Abstract]
Target asset allocation percentage	20.00%	[11]
Total weighted average asset allocation	18.00%	[11]	14.00%	[11]
Other Postretirement Benefit Plans Defined Benefit [Member] | Exelon Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Benefit obligation increase (decrease) reflecting actual census data	(39,000,000)
Other Postretirement Benefit Plans Defined Benefit [Member] | Constellation Legacy Benefit Plans [Member]
Valuation Adjustment Impact [Abstract]
Benefit obligation increase (decrease) reflecting actual census data	(12,000,000)
Other Postretirement Benefit Plans Defined Benefit [Member] | Business Services Company [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	5,000,000	[12]	24,000,000	[12]	20,000,000	[12]
Other Postretirement Benefit Plans Defined Benefit [Member] | Exelon Generation Co L L C [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	30,000,000	[12]	135,000,000	[12]	121,000,000	[12]
Other Postretirement Benefit Plans Defined Benefit [Member] | Commonwealth Edison Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	4,000,000	[12]	119,000,000	[12]	108,000,000	[12]
Other Postretirement Benefit Plans Defined Benefit [Member] | PECO Energy Co [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	20,000,000	[12]	33,000,000	[12]	28,000,000	[12]
Other Postretirement Benefit Plans Defined Benefit [Member] | Baltimore Gas and Electric Company [Member]
Pension And Other Postretirement Benefit Contributions [Abstract]
Pension and non-pension postretirement benefit contributions	$ 24,000,000	[12],[13]	$ 12,000,000	[12],[13]

[1] These amounts primarily represent amounts billed to Exelon's subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO or BGE amounts above. As of December 31, 2012, ComEd and BGE each reported a regulatory asset of $1 million related to their BSC-billed portion of the second quarter 2012 contractual termination benefit charge.

[2] The amounts included in capital and operating and maintenance expense for the years ended December 31, 2012 and 2011 include $12 million and $51 million, respectively, in costs incurred prior to the closing of Exelon’s merger with Constellation on March 12, 2012. These amounts are not included in Exelon’s capital expenditures and operating and maintenance expense for the years ended December 31, 2012 and 2011.

[3] BGE’s pension and other postretirement benefit costs for the year ended December 31, 2012 include a $3 million contractual termination benefit charge, which was recorded as a regulatory asset as of December 31, 2012.

[4] Represents cash settlements only.

[5] Exelon's other postretirement benefits paid for the year ended December 31, 2012 are net of $1.3 million of reinsurance proceeds received from the Department of Health and Human Services as part of the Early Retiree Reinsurance Program pursuant to the Affordable Care Act of 2010. In 2013, the Program was no longer accepting applications for reimbursement

[6] ComEd and BGE established regulatory assets of $1 million and $4 million, respectively, for their portion of the contractual termination benefit charge in 2012.

[7] Of the $1,753 million gain related to pension benefits, $1,071 million and $682 million were recognized in AOCI and regulatory assets, respectively, during 2013. Of the $677 million gain related to other postretirement benefits, $352 million and $325 million were recognized in AOCI and regulatory assets (liabilities), respectively, during 2013. Of the $1,188 million loss related to pension benefits, $283 million and $904 million were recognized in AOCI and regulatory assets, respectively, during 2012. Of the $120 million loss related to other postretirement benefits, $39 million and $81 million were recognized in AOCI and regulatory assets, respectively, during 2012. Of the $399 million loss related to pension benefits, $181 million and $218 million were recognized in AOCI and regulatory assets, respectively, during 2011. Of the $37 million loss related to other postretirement benefits, $13 million and $24 million were recognized in AOCI and regulatory assets, respectively, during 2011.

[8] Of the $6,254 million related to pension benefits, $3,523 million and $2,731 million are included in AOCI and regulatory assets, respectively, at December 31, 2013. Of the $401 million related to other postretirement benefits, $161 million and $240 million are included in AOCI and regulatory assets (liabilities), respectively, at December 31, 2013. Of the $8,007 million related to pension benefits, $4,594 million and $3,413 million are included in AOCI and regulatory assets, respectively, at December 31, 2012. Of the $1,078 million related to other postretirement benefits, $514 million and $564 million are included in AOCI and regulatory assets, respectively, at December 31, 2012.

[9] Of the $441 million related to pension benefits at December 31, 2013, $232 million and $209 million are expected to be amortized from AOCI and regulatory assets in 2013, respectively. Of the $16 million related to other postretirement benefits at December 31, 2013, $7 million and $9 million are expected to be amortized from AOCI and regulatory assets in 2013, respectively

[10] The increase in 2011 pension contributions was related to Exelon’s $2.1 billion contribution to its pension plans as a result of accelerated cash benefits associated with the Tax Relief Act of 2010.

[11] Alternative investments include private equity, hedge funds and real estate

[12] The Registrants present the cash contributions above net of Federal subsidy payments received on each of their respective Consolidated Statements of Cash Flows. Exelon, Generation, ComEd, PECO, and BGE received Federal subsidy payments of $10 million, $5 million, $4 million, $1 million and $2 million, respectively, in 2012, and $11 million, $5 million, $4 million, $1 million and $3 million, respectively, in 2011. Effective January 1, 2013, Exelon is no longer receiving this subsidy

[13] BGE’s pension benefit contributions for 2012 and 2011 exclude $0 million and $54 million, respectively, of pension contributions made by BGE prior to the closing of Exelon’s merger with Constellation on March 12, 2012. BGE’s other postretirement benefit payments for 2012 and 2011 exclude $4 million and $13 million, respectively, of other postretirement benefit payments made by BGE prior to the closing of Exelon’s merger with Constellation on March 12, 2012. These pre-merger contributions are not included in Exelon’s financial statements but are reflected in BGE’s financial statements.