Regulatory Matters (Details) (USD $)	3 Months Ended																																																																															3 Months Ended		1 Months Ended	3 Months Ended			12 Months Ended																																																								3 Months Ended																																																													3 Months Ended		3 Months Ended			12 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013		Mar. 31, 2014 Nuclear Decommissioning [Member]	Dec. 31, 2013 Nuclear Decommissioning [Member]	Mar. 31, 2014 Removal Costs [Member]	Dec. 31, 2013 Removal Costs [Member]	Mar. 31, 2014 Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2013 Energy Efficiency Demand Response Programs [Member]	Mar. 31, 2014 Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2013 Electric Transmission And Distribution Tax Repairs [Member]	Mar. 31, 2014 Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Over Recovered Energy And Transmission Costs [Member]	Mar. 31, 2014 Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2013 Over-Recovered Universal Service Fund Costs [Member]	Mar. 31, 2014 Revenue subject to refund [Member]		Dec. 31, 2013 Revenue subject to refund [Member]		Mar. 31, 2014 Over Recovered Decoupling Revenue [Member]		Dec. 31, 2013 Over Recovered Decoupling Revenue [Member]		Dec. 31, 2013 Gas Distribution Tax Repairs [Member]	Mar. 31, 2014 Regulatory Liabilities Other [Member]	Dec. 31, 2013 Regulatory Liabilities Other [Member]	Mar. 31, 2014 Dlc Program Cost [Member]	Dec. 31, 2013 Dlc Program Cost [Member]	Mar. 31, 2014 Energy Efficiency Phase [Member]	Dec. 31, 2013 Energy Efficiency Phase [Member]	Mar. 31, 2014 Other Postretirement Benefits [Member]	Dec. 31, 2013 Other Postretirement Benefits [Member]	Mar. 31, 2014 Other Postretirement Benefits [Member]	Dec. 31, 2013 Other Postretirement Benefits [Member]	Mar. 31, 2014 Deferred Income Taxes [Member]	Dec. 31, 2013 Deferred Income Taxes [Member]	Mar. 31, 2014 AMI Expenses [Member]	Dec. 31, 2013 AMI Expenses [Member]	Dec. 31, 2013 AMI Meter Events [Member]	Mar. 31, 2014 Under Recovered Distribution Service Costs [Member]	Dec. 31, 2013 Under Recovered Distribution Service Costs [Member]	Mar. 31, 2014 Debt Costs [Member]	Dec. 31, 2013 Debt Costs [Member]	Mar. 31, 2014 Fair Value Of Long Term Debt [Member]		Dec. 31, 2013 Fair Value Of Long Term Debt [Member]		Mar. 31, 2014 Fair Value Of Supply Contract [Member]		Dec. 31, 2013 Fair Value Of Supply Contract [Member]		Mar. 31, 2014 Severance [Member]	Dec. 31, 2013 Severance [Member]	Mar. 31, 2014 Asset Retirement Obligations [Member]	Dec. 31, 2013 Asset Retirement Obligations [Member]	Mar. 31, 2014 MGP Remediation Costs [Member]	Dec. 31, 2013 MGP Remediation Costs [Member]	Mar. 31, 2014 RTO Startup Costs [Member]	Dec. 31, 2013 RTO Startup Costs [Member]	Mar. 31, 2014 Under Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2013 Under Recovered Uncollectible Accounts Expense [Member]	Mar. 31, 2014 Renewable Energy And Associated REC [Member]	Dec. 31, 2013 Renewable Energy And Associated REC [Member]	Mar. 31, 2014 Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Under Recovered Energy And Transmission Costs [Member]	Mar. 31, 2014 Deferred Storm Costs [Member]	Dec. 31, 2013 Deferred Storm Costs [Member]	Mar. 31, 2014 Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2013 Electric Generation Related Regulatory Asset [Member]	Mar. 31, 2014 Rate Stabilization Deferral [Member]	Dec. 31, 2013 Rate Stabilization Deferral [Member]	Mar. 31, 2014 Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2013 Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2014 Merger Integration Costs [Member]	Dec. 31, 2013 Merger Integration Costs [Member]	Mar. 31, 2014 Regulatory Assets [Member]	Dec. 31, 2013 Regulatory Assets [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] Regulatory Liabilities Other [Member]	Sep. 30, 2008 Commonwealth Edison Co [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member]		Mar. 31, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]		Dec. 31, 2012 Commonwealth Edison Co [Member]	Feb. 29, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2010 Commonwealth Edison Co [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Removal Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Removal Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Revenue subject to refund [Member]		Dec. 31, 2013 Commonwealth Edison Co [Member] Revenue subject to refund [Member]		Mar. 31, 2014 Commonwealth Edison Co [Member] Other Postretirement Benefits [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] AMI Expenses [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] AMI Expenses [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Debt Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Debt Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Fair Value Of Long Term Debt [Member]		Mar. 31, 2014 Commonwealth Edison Co [Member] Fair Value Of Supply Contract [Member]		Dec. 31, 2013 Commonwealth Edison Co [Member] Fair Value Of Supply Contract [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Severance [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Severance [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Under Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Under Recovered Uncollectible Accounts Expense [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Deferred Storm Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Electric Generation Related Regulatory Asset [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Merger Integration Costs [Member]	Mar. 31, 2014 Commonwealth Edison Co [Member] Regulatory Assets [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member] Regulatory Assets [Member]	Mar. 31, 2014 PECO Energy Co [Member] SmartMeters		Mar. 31, 2013 PECO Energy Co [Member]	Dec. 31, 2013 PECO Energy Co [Member]		Mar. 31, 2014 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2013 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2013 PECO Energy Co [Member] Removal Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Dec. 31, 2013 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Mar. 31, 2014 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Gas Distribution Tax Repairs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Gas Distribution Tax Repairs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Regulatory Liabilities Other [Member]	Dec. 31, 2013 PECO Energy Co [Member] Regulatory Liabilities Other [Member]	Mar. 31, 2014 PECO Energy Co [Member] Dlc Program Cost [Member]	Dec. 31, 2013 PECO Energy Co [Member] Dlc Program Cost [Member]	Mar. 31, 2014 PECO Energy Co [Member] Energy Efficiency Phase [Member]	Dec. 31, 2013 PECO Energy Co [Member] Energy Efficiency Phase [Member]	Mar. 31, 2014 PECO Energy Co [Member] Other Postretirement Benefits [Member]	Mar. 31, 2014 PECO Energy Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2013 PECO Energy Co [Member] Deferred Income Taxes [Member]	Mar. 31, 2014 PECO Energy Co [Member] AMI Expenses [Member]	Dec. 31, 2013 PECO Energy Co [Member] AMI Expenses [Member]	Dec. 31, 2013 PECO Energy Co [Member] AMI Meter Events [Member]	Mar. 31, 2014 PECO Energy Co [Member] Under Recovered Distribution Service Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Debt Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Debt Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Fair Value Of Long Term Debt [Member]		Mar. 31, 2014 PECO Energy Co [Member] Fair Value Of Supply Contract [Member]		Dec. 31, 2013 PECO Energy Co [Member] Fair Value Of Supply Contract [Member]	Mar. 31, 2014 PECO Energy Co [Member] Severance [Member]	Dec. 31, 2013 PECO Energy Co [Member] Severance [Member]	Mar. 31, 2014 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2013 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Mar. 31, 2014 PECO Energy Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] MGP Remediation Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] RTO Startup Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Under Recovered Uncollectible Accounts Expense [Member]	Mar. 31, 2014 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Deferred Storm Costs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Deferred Storm Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2013 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Mar. 31, 2014 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2013 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Mar. 31, 2014 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Merger Integration Costs [Member]	Mar. 31, 2014 PECO Energy Co [Member] Regulatory Assets [Member]	Dec. 31, 2013 PECO Energy Co [Member] Regulatory Assets [Member]	Mar. 31, 2014 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Jun. 01, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] MW SmartMeters		Mar. 31, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]		Sep. 30, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Nuclear Decommissioning [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution Tax Repairs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]		Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Gas Energy And Transmission Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Over-Recovered Universal Service Fund Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Revenue [Member]		Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Revenue [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Electric Revenue [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Gas Revenue [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Gas Revenue [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Regulatory Liabilities Other [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Over Recovered Electric Energy And Transmission Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Other Postretirement Benefits [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] AMI Meter Events [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Under Recovered Distribution Service Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Fair Value Of Long Term Debt [Member]		Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Fair Value Of Supply Contract [Member]		Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Fair Value Of Supply Contract [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Severance [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Severance [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Asset Retirement Obligations [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Asset Retirement Obligations [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] RTO Startup Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Under Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Uncollectible Accounts Expense [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]		Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Electric Energy And Transmission Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Merger Integration Costs [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Merger Integration Costs [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] Regulatory Assets [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Regulatory Assets [Member]	Mar. 31, 2014 Exelon Corporate [Member] Gas Distribution Tax Repairs [Member]
Purchase Of Receivables [Abstract]
POR gross receivables	$ 330,000,000	[1]		$ 263,000,000	[1]																																																																														$ 125,000,000	[1]		$ 105,000,000	[1]																																																							$ 93,000,000	[1]		$ 72,000,000	[1]																																																											$ 112,000,000	[1]		$ 86,000,000	[1]
POR Allowance for uncollectible accounts	(36,000,000)	[2]		(30,000,000)	[2]																																																																														(19,000,000)	[2]		(16,000,000)	[2]																																																							(10,000,000)	[2]		(7,000,000)	[2]																																																											(7,000,000)	[2]		(7,000,000)	[2]
POR net receivables	294,000,000			233,000,000																																																																															106,000,000			89,000,000																																																								83,000,000			65,000,000																																																												105,000,000			79,000,000
Energy Infrastructure Modernization Act [Abstract]
Current length of state legislation enacted			10 years
Increased revenue requirement																																																																																			275,000,000
Expected revenue adjustment for prior year																																																																																			98,000,000
Expected revenue adjustment for current year																																																																																			177,000,000
Excess basis points over treasury after year one																																																																																			5.80%
Senate Bill [Abstract]
Next 6 months Projected Revenue																																																																																			15,000,000
Year 2 Projected Revenue	65,000,000
Next 12 months Projected CapEx	40,000,000
Year 2 Projected CapEx	45,000,000
Next 6 months estimated refund																																																																																			14,000,000
Illinois Settlement Agreement [Abstract]
Annual energy savings requirement																																																																																																																																																																																																											3.00%
Demand response peak demand reduction																																																																																																																																																																																																												4.50%
Distribution Rate Case [Abstract]
Requested increase in electric revenues																																																																																										396,000,000																																																																																																																								101,000,000
Adjustment to Requested increase in electric revenues																																																																																						343,000,000
Recovery request for Operating and Maintenance expenses of AMI Pilot Program																																																																																						40,000,000
Requested increase in gas revenues																																																																																																																																																																																																																		30,000,000
Requested rate of return on common equity																																																																																						11.50%
Rate of return on common equity electric distribution																																																																																		0.103%																																																																																																																											9.75%
Rate of return on common equity gas distribution																																																																																																																																																																																																													9.60%
Increase in electric delivery service revenue resulting from rate case settlement or order.																																																																																						143,000,000																																																																																																																							81,000,000			34,000,000
Increase in gas delivery service revenue resulting from rate case settlement or order.																																																																																																																																																																																																													32,000,000			12,000,000
Regulatory Assets Transfer Changes																																																																																																																																																																																																													8,000,000
Severance Recovered Through Distribution Rates																																																																																																																																																																																																													20,000,000
ComEd's proposed increase to net distribution revenue requirement related to uncollectable account expense																																																																																						22,000,000
Requested Rate Of Return Common Equity Electric Distribution																																																																																						10.5																																																																																																																							10.50
Requested Rate Of Return Common Equity Gas Distribution																																																																																																																																																																																																													10.35
Appeal of 2007 Illinois Electric Distribution Rate Case [Abstract]
Increase in electric delivery service revenue requirement resulting from regulatory order in rate case																																																																																		274,000,000
Estimated Refund Obligation To Customers																																																																																									37,000,000
Annual Transmission Formula Rate Update [Abstract]
Gross transmission revenue requirement																																																																																			524,000,000		488,000,000																																																																																																																								167,000,000			158,000,000
Transmission revenue true up																																																																																			11,000,000		25,000,000																																																																																																																								4,000,000			1,000,000
Net transmission revenue requirement																																																																																			535,000,000		513,000,000																																																																																																																								171,000,000			157,000,000
Smart Meter and Smart Grid Investments [Abstract]
Estimated number of smart meters to be installed																																																																																																																																														1,600,000																																																															2,000,000
Expected number of smart meters to be deployed during the first phase of Smart Meter Installment Plan																																																																																																																																														600,000
Revised spend on its Smart Meter Procurement and Installation Plan																																																																																																																																														595,000,000
Spend on smart grid investments																																																																																																																																														120,000,000
Smart meter spend to date																																																																																																																																														457,000,000
Smart grid infrastructure spend to date																																																																																																																																														119,000,000
Total smart grid and smart meter investment grant amount																																																																																																																																														200,000,000
Smart meter investment grant awarded																																																																																																																																														140,000,000
Smart grid investment grant awarded																																																																																																																																														60,000,000																																																															200,000,000
Reimbursements received from the DOE																																																																																																																																														197,000,000																																																															200,000,000
Outstanding reimbursable DOE Smart Grid Investment Grant expenditures																																																																																																																																														3,000,000																																																															23,000,000
Regulatory assets for original smart meters purchased																																																																																																																																														17,000,000
Carrying value of originally installed Smart Meters, net of reimbursements from DOE																																																																																																																																														17,000,000
VendorRefund																																																																																																																																														12,000,000
Amount of reimbursements received from the DOE applied to the originally installed Smart Meters.																																																																																																																																														16,000,000
Total Projected smart meter smart grid spend																																																																																																																																																																																																													480,000,000
Current Year AMI Events Balance																																																																																																																																																	5,000,000
Depreciation Related To Original Meters																																																																																																																																														2,000,000
DOE Cash Payable to Sub Receipients																																																																																																																																														4,000,000
Upfront fee for opt-out of Smart Meter																																																																																																																																																																																																													75
RecurringFees																																																																																																																																																																																																													11
New Electric Generation [Abstract]
Megawatt capacity of new generating plant																																																																																																																																																																																																													700
Energy Efficiency Program [Abstract]
Proposed funding of estimated costs associated with DLC demand program due to modification of incentive levels for other Phase II programs.																																																																																																																																																																																																											10,000,000
Advanced metering infrastructure pilot program [Abstract]
Collections Under Rider Amp																																																																																						24,000,000
RegulatoryLiabilityUnderRiderAmp																																																																																			400,000
RefundAMP																																																																																			14,600,000
Authorized Return On Rate Base [Abstract]
Weighted Average Debt And Equity Return Electric Distribution																																																																																						0.0706%		0.0704%
Weighted Average Debt And Equity Return																																																																																			8.62%		8.70%																																																																																																																								8.53%		8.35%
Rate Of Return On Common Equity																																																																																			11.50%			0.0925%		0.092%																																																																																																																					10.80%			11.30%
Rate Of Return On Common Equity in FERC Complaint																																																																																																																																																																																																													8.70%
Potential refund resulting from the FERC Comlaint																																																																																																																																																																																																													10,000,000
Common Equity Component Cap																																																																																			55.00%
Regulatory Assets And Liabilities Other Disclosures [Abstract]
Over under recovered transmission costs																																																																																																																																														11,000,000
Over under recovered electric supply costs																																																																																																																																														32,000,000			34,000,000
Over under recovered gas supply costs																																																																																																																																														0			16,000,000
Amortization of rate stabilization deferral	20,000,000		30,000,000																																																																																																																																																																																																										20,000,000		30,000,000
Recovered portion of regulatory assets	72,000,000		61,000,000																																																																																30,000,000		30,000,000																																																									2,000,000		2,000,000																																																													38,000,000		29,000,000
Maryland Electric And Natural Gas Distribution Rate Cases [Abstract]
Captial and OM estimates current year																																																																																																																																																																																																													14,800,000
Revenue Requirment																																																																																																																																																																																																													1,400,000
License Renewals [Abstract]
Minimum Purchase Obligation	20,000,000																																																																															20,000,000
Maximum Purchase Obligation	30,000,000																																																																															30,000,000
License Costs	34,000,000																																																																															34,000,000
Regulatory Asset [Line Items]
Noncurrent regulatory assets	5,863,000,000			5,910,000,000																															2,777,000,000	2,794,000,000	1,474,000,000	1,459,000,000	186,000,000	159,000,000	5,000,000	262,000,000	285,000,000	54,000,000	56,000,000	206,000,000	[3]	219,000,000	[3]	0	[4]	0	[4]	12,000,000	12,000,000	108,000,000	102,000,000	201,000,000	212,000,000	0	0	74,000,000	48,000,000	155,000,000	176,000,000	0		2,000,000	3,000,000	27,000,000	30,000,000	133,000,000	154,000,000	146,000,000	148,000,000	8,000,000	9,000,000	38,000,000	39,000,000				918,000,000			933,000,000																			0	67,000,000	65,000,000	43,000,000	35,000,000	262,000,000	285,000,000	51,000,000	53,000,000	0	[3]	0	[4]	0	0	0	72,000,000	67,000,000	168,000,000	178,000,000	0	0	74,000,000	48,000,000	155,000,000	176,000,000	0		0	0	0	0	0	0		26,000,000	26,000,000	1,465,000,000			1,448,000,000																							0	1,333,000,000	1,317,000,000	65,000,000	58,000,000	5,000,000	0	3,000,000	3,000,000	0	[3]	0	[4]		0	0	25,000,000	25,000,000	32,000,000	33,000,000	0	0	0	0	0	0	0	0	0	0	0	0		7,000,000	7,000,000			504,000,000			524,000,000																						0	74,000,000	77,000,000	78,000,000	66,000,000	0	0	8,000,000	8,000,000	0	[3]	0	[4]		12,000,000	12,000,000	11,000,000	10,000,000	1,000,000	1,000,000	0	0	0	0	0			2,000,000	3,000,000	27,000,000	30,000,000	133,000,000	154,000,000	146,000,000	148,000,000	8,000,000	9,000,000	4,000,000	6,000,000
Current regulatory assets	768,000,000			760,000,000																															218,000,000	221,000,000	14,000,000	10,000,000	6,000,000	5,000,000		197,000,000	178,000,000	12,000,000	12,000,000	6,000,000	[3]	0		9,000,000	[4]	12,000,000	[4]	10,000,000	16,000,000	1,000,000	1,000,000	44,000,000	40,000,000	2,000,000	2,000,000	0	0	13,000,000	17,000,000	51,000,000	53,000,000	3,000,000	3,000,000	13,000,000	13,000,000	72,000,000	71,000,000	57,000,000	73,000,000	2,000,000	2,000,000	38,000,000	31,000,000				340,000,000			329,000,000																			0	2,000,000	2,000,000	6,000,000	5,000,000	197,000,000	178,000,000	9,000,000	9,000,000	0	[3]	0	[4]	0	6,000,000	12,000,000	1,000,000	1,000,000	37,000,000	33,000,000	2,000,000	2,000,000	0	0	13,000,000	17,000,000	50,000,000	52,000,000	0	0	0		0	0	0	17,000,000	18,000,000	28,000,000			17,000,000																							0	0		0			0	3,000,000	3,000,000	0	[3]	0	[4]	0	0	0	0	0	6,000,000	6,000,000	0	0	1,000,000	0	0	0	0	0	0	0	0	0	0	18,000,000	8,000,000			168,000,000			181,000,000																						0	12,000,000	8,000,000	0	0	0	0	1,000,000	1,000,000	0	[3]	1,000,000		11,000,000	4,000,000	4,000,000	0		1,000,000	1,000,000	0	0	0	0	1,000,000	[5]	7,000,000	3,000,000	3,000,000	13,000,000	13,000,000	72,000,000	71,000,000	57,000,000	73,000,000	2,000,000	2,000,000	3,000,000	4,000,000
Net regulatory asset																																																																																																														459,000,000	463,000,000
Regulatory Liabilities [Line Items]
Regulatory Liability Current	336,000,000			327,000,000			0	105,000,000	99,000,000	40,000,000	53,000,000	22,000,000	20,000,000	76,000,000	78,000,000	7,000,000	8,000,000	38,000,000	[6]	38,000,000	[6]	35,000,000	[7]	16,000,000	[7]	8,000,000	2,000,000	4,000,000	1,000,000	1,000,000			2,000,000	2,000,000																																																	158,000,000			170,000,000						0	81,000,000	78,000,000	39,000,000	45,000,000	0	0	9,000,000	0	38,000,000	[6]	38,000,000	[6]																																						84,000,000			106,000,000			0	0	1,000,000	8,000,000	22,000,000	20,000,000	43,000,000	[8]	58,000,000	[8]	7,000,000	8,000,000	8,000,000	8,000,000	2,000,000	3,000,000	1,000,000	1,000,000																																								92,000,000			48,000,000			0	24,000,000	21,000,000	0	0	33,000,000	[5]	11,000,000	30,000,000	0	35,000,000	[7]	16,000,000	[7]	14,000,000	21,000,000	9,000,000	0	3,000,000																																								8,000,000
Noncurrent regulatory liabilities	4,458,000,000			4,388,000,000		2,774,000,000	2,740,000,000	1,440,000,000	1,423,000,000		0	108,000,000	114,000,000	10,000,000	0		0									37,000,000	1,000,000		11,000,000	10,000,000	31,000,000	21,000,000	47,000,000	43,000,000																																															0		3,566,000,000			3,512,000,000					2,319,000,000	2,293,000,000	1,237,000,000	1,219,000,000	0	0	0	10,000,000	0	0																																										641,000,000			629,000,000		455,000,000	447,000,000	0		0	108,000,000	114,000,000			0			0	36,000,000	37,000,000			11,000,000	10,000,000	31,000,000	21,000,000																																						203,000,000			204,000,000			0	203,000,000	204,000,000	0	0			0		0																																																	36,000,000
Regulatory Liabilities Table Footnote Data [Abstract]
Electric Transmission Costs Under-Recovery																																																																																																																																																	$ 8,000,000

[1] PECO's gas POR program became effective on January 1, 2012 and includes a 1% discount on purchased receivables in order to recover the implementation costs of the program. If the costs are not fully recovered when PECO files its next gas distribution rate case, PECO will propose a mechanism to recover the remaining implementation costs as a distribution charge to low volume transportation customers or apply future discounts on purchased receivables from natural gas suppliers serving those customers.

[2] For ComEd and BGE, reflects the incremental allowance for uncollectible accounts recorded, which is in addition to the purchase discount. For ComEd, the incremental uncollectible accounts expense is recovered through its Purchase of Receivables with Consolidated Billing (PORCB) tariff.

[3] Represents the regulatory asset recorded at Exelon Corporate for the difference in the fair value of the long-term debt of BGE as of the merger date. The asset is amortized over the life of the underlying debt. See Note 8 – Debt and Credit Agreements for additional information.

[4] Represents the regulatory asset recorded at Exelon Corporate representing the fair value of BGE's supply contracts as of the close of the merger date. BGE is allowed full recovery of the costs of its electric and gas supply contracts through approved, regulated rates. The asset is amortized over a period of approximately 3 years.

[5] . Relates to $3 million of over-recovered electric supply costs and $30 million of over-recovered natural gas supply costs as of March 31, 2014. As of December 31, 2013, includes $1 million of under-recovered electric supply costs and $11 million of over-recovered natural gas supply costs.

[6] Primarily represents the regulatory liability for revenue subject to refund recorded pursuant to the ICC’s order in the 2007 Rate Case. See Note 3 – Regulatory Matters of the Exelon 2013 Form 10-K. for further information.

[7] Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of March 31, 2014, BGE had a regulatory liability of $14 million related to over-recovered electric revenue decoupling and $21 million related to over-recovered natural gas revenue decoupling. As of December 31, 2013, BGE had a regulatory liability of $7 million related to over-recovered electric revenue decoupling and $9 million related to over-recovered natural gas revenue decoupling

[8] Includes $32 million related to the DSP program, $0 million related to the over-recovered natural gas costs under the PGC and $11 million related to over-recovered electric transmission costs as of March 31, 2014. As of December 31, 2013, includes $34 million related to the DSP program, $8 million related to the over-recovered electric transmission costs and $16 million related to the over-recovered natural gas costs under the PGC.