Regulatory Matters (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended																																																																																								6 Months Ended			1 Months Ended	6 Months Ended			12 Months Ended																																																																	6 Months Ended																																																																									0 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended			12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Dec. 31, 2012		Jun. 30, 2013 Nuclear Decommissioning [Member]	Dec. 31, 2012 Nuclear Decommissioning [Member]	Jun. 30, 2013 Removal Costs [Member]	Dec. 31, 2012 Removal Costs [Member]	Jun. 30, 2013 Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2012 Energy Efficiency Demand Response Programs [Member]	Jun. 30, 2013 Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 Over Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Over Recovered Energy And Transmission Costs [Member]	Jun. 30, 2013 Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 Over-Recovered AEPS Costs [Member]	Jun. 30, 2013 Revenue subject to refund [Member]		Dec. 31, 2012 Revenue subject to refund [Member]		Jun. 30, 2013 Over Recovered Decoupling Revenue [Member]		Dec. 31, 2012 Over Recovered Decoupling Revenue [Member]		Dec. 31, 2012 Gas Distribution Tax Repairs [Member]	Jun. 30, 2013 Regulatory Liabilities Other [Member]	Jun. 30, 2013 Dlc Program Cost [Member]	Jun. 30, 2013 Energy Efficiency Phase [Member]	Jun. 30, 2013 Pension and Other Postretirement Benefits [Member]		Dec. 31, 2012 Pension and Other Postretirement Benefits [Member]		Jun. 30, 2013 Deferred Income Taxes [Member]	Dec. 31, 2012 Deferred Income Taxes [Member]	Jun. 30, 2013 AMI Expenses [Member]	Dec. 31, 2012 AMI Expenses [Member]	Jun. 30, 2013 AMI Meter Events [Member]	Dec. 31, 2012 AMI Meter Events [Member]	Jun. 30, 2013 Under Recovered Distribution Service Costs [Member]	Dec. 31, 2012 Under Recovered Distribution Service Costs [Member]	Jun. 30, 2013 Debt Costs [Member]	Dec. 31, 2012 Debt Costs [Member]	Jun. 30, 2013 Fair Value Of Long Term Debt [Member]		Dec. 31, 2012 Fair Value Of Long Term Debt [Member]		Jun. 30, 2013 Fair Value Of Supply Contract [Member]		Dec. 31, 2012 Fair Value Of Supply Contract [Member]		Jun. 30, 2013 Severance [Member]	Dec. 31, 2012 Severance [Member]	Jun. 30, 2013 Asset Retirement Obligations [Member]	Dec. 31, 2012 Asset Retirement Obligations [Member]	Jun. 30, 2013 MGP Remediation Costs [Member]	Dec. 31, 2012 MGP Remediation Costs [Member]	Jun. 30, 2013 RTO Startup Costs [Member]	Dec. 31, 2012 RTO Startup Costs [Member]	Jun. 30, 2013 Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2012 Under Recovered Universal Service Fund Costs Member [Member]	Jun. 30, 2013 Under Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Financial Swap with Generation [Member]	Jun. 30, 2013 Renewable Energy And Associated REC [Member]	Dec. 31, 2012 Renewable Energy And Associated REC [Member]	Jun. 30, 2013 Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Under Recovered Energy And Transmission Costs [Member]	Jun. 30, 2013 DSP Program Electric Procurement Contracts [Member]	Jun. 30, 2013 DSP II Program Electric Procurement Contracts [Member]	Dec. 31, 2012 DSP Program costs [Member]	Dec. 31, 2012 DSP II Program Costs [Member]	Jun. 30, 2013 Deferred Storm Costs [Member]	Dec. 31, 2012 Deferred Storm Costs [Member]	Jun. 30, 2013 Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2012 Electric Generation Related Regulatory Asset [Member]	Jun. 30, 2013 Rate Stabilization Deferral [Member]	Dec. 31, 2012 Rate Stabilization Deferral [Member]	Jun. 30, 2013 Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Under Recovered Decoupling Revenue [Member]		Dec. 31, 2012 Under Recovered Decoupling Electric Revenue [Member]	Jun. 30, 2013 Merger Integration Costs [Member]		Jun. 30, 2013 Other Regulatory Assets [Member]	Dec. 31, 2012 Other Regulatory Assets [Member]	Jun. 30, 2012 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Regulatory Liabilities Other [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] Under Recovered Uncollectible Accounts Expense [Member]	Sep. 30, 2008 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]		Jun. 30, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]		Dec. 31, 2011 Commonwealth Edison Co [Member]	Feb. 29, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2010 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Removal Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Removal Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Over-Recovered AEPS Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Revenue subject to refund [Member]		Dec. 31, 2012 Commonwealth Edison Co [Member] Revenue subject to refund [Member]		Jun. 30, 2013 Commonwealth Edison Co [Member] Pension and Other Postretirement Benefits [Member]		Jun. 30, 2013 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] AMI Expenses [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] AMI Expenses [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] AMI Meter Events [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Debt Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Debt Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Fair Value Of Long Term Debt [Member]		Jun. 30, 2013 Commonwealth Edison Co [Member] Fair Value Of Supply Contract [Member]		Dec. 31, 2012 Commonwealth Edison Co [Member] Fair Value Of Supply Contract [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Severance [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Severance [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Under Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Financial Swap with Generation [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Financial Swap with Generation [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] DSP Program Electric Procurement Contracts [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] DSP II Program Electric Procurement Contracts [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Deferred Storm Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Electric Generation Related Regulatory Asset [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Under Recovered Decoupling Electric Revenue [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Merger Integration Costs [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member] Other Regulatory Assets [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member] Other Regulatory Assets [Member]	Jun. 30, 2013 PECO Energy Co [Member] SmartMeters		Jun. 30, 2012 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]		Jun. 30, 2013 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2012 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2012 PECO Energy Co [Member] Removal Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Dec. 31, 2012 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Jun. 30, 2013 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Over-Recovered AEPS Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Gas Distribution Tax Repairs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Gas Distribution Tax Repairs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Regulatory Liabilities Other [Member]	Jun. 30, 2013 PECO Energy Co [Member] Dlc Program Cost [Member]	Jun. 30, 2013 PECO Energy Co [Member] Energy Efficiency Phase [Member]	Jun. 30, 2013 PECO Energy Co [Member] Pension and Other Postretirement Benefits [Member]		Dec. 31, 2012 PECO Energy Co [Member] Pension and Other Postretirement Benefits [Member]		Jun. 30, 2013 PECO Energy Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2012 PECO Energy Co [Member] Deferred Income Taxes [Member]	Jun. 30, 2013 PECO Energy Co [Member] AMI Expenses [Member]	Dec. 31, 2012 PECO Energy Co [Member] AMI Expenses [Member]	Jun. 30, 2013 PECO Energy Co [Member] AMI Meter Events [Member]	Dec. 31, 2012 PECO Energy Co [Member] AMI Meter Events [Member]	Jun. 30, 2013 PECO Energy Co [Member] Under Recovered Distribution Service Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Debt Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Debt Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Fair Value Of Long Term Debt [Member]		Jun. 30, 2013 PECO Energy Co [Member] Fair Value Of Supply Contract [Member]		Dec. 31, 2012 PECO Energy Co [Member] Fair Value Of Supply Contract [Member]	Jun. 30, 2013 PECO Energy Co [Member] Severance [Member]	Dec. 31, 2012 PECO Energy Co [Member] Severance [Member]	Jun. 30, 2013 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2012 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Jun. 30, 2013 PECO Energy Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] MGP Remediation Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] RTO Startup Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2012 PECO Energy Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Jun. 30, 2013 PECO Energy Co [Member] Financial Swap with Generation [Member]	Jun. 30, 2013 PECO Energy Co [Member] Renewable Energy And Associated REC [Member]	Jun. 30, 2013 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]		Jun. 30, 2013 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]	Dec. 31, 2012 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]	Jun. 30, 2013 PECO Energy Co [Member] DSP II Program Electric Procurement Contracts [Member]	Dec. 31, 2012 PECO Energy Co [Member] DSP II Program Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Deferred Storm Costs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Deferred Storm Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2012 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Jun. 30, 2013 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2012 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Jun. 30, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 PECO Energy Co [Member] Under Recovered Decoupling Electric Revenue [Member]	Jun. 30, 2013 PECO Energy Co [Member] Merger Integration Costs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Other Regulatory Assets [Member]	Dec. 31, 2012 PECO Energy Co [Member] Other Regulatory Assets [Member]	Jun. 01, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Jun. 30, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Mar. 31, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] MW SmartMeters		Jun. 30, 2012 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Nuclear Decommissioning [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Gas Energy And Transmission Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over-Recovered AEPS Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Revenue [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Revenue [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Electric Revenue [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Gas Revenue [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Decoupling Gas Revenue [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Regulatory Liabilities Other [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Over Recovered Electric Energy And Transmission Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Pension and Other Postretirement Benefits [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Pension and Other Postretirement Benefits [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] AMI Meter Events [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] AMI Meter Events [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Distribution Service Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Fair Value Of Long Term Debt [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Fair Value Of Supply Contract [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Severance [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Severance [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Asset Retirement Obligations [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] RTO Startup Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Universal Service Fund Costs Member [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Uncollectible Accounts Expense [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Financial Swap with Generation [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Renewable Energy And Associated REC [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Electric Energy And Transmission Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Gas Energy And Transmission Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] DSP Program Electric Procurement Contracts [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] DSP Program Electric Procurement Contracts [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] DSP II Program Electric Procurement Contracts [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] DSP II Program Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Decoupling Revenue [Member]		Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Decoupling Electric Revenue [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Merger Integration Costs [Member]		Jun. 30, 2013 Baltimore Gas and Electric Company [Member] Other Regulatory Assets [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member] Other Regulatory Assets [Member]	Jun. 30, 2013 Exelon Corporate [Member] Gas Distribution Tax Repairs [Member]	Jun. 30, 2013 Exelon Corporate [Member] AMI Meter Events [Member]
Purchase Of Receivables [Abstract]
POR gross receivables	$ 230	[1]		$ 191	[1]																																																																																								$ 87	[1]		$ 55	[1]																																																																$ 70	[1]		$ 65	[1]																																																																								$ 73	[1]		$ 71	[1]
POR Allowance for uncollectible accounts	(24)	[2]		(21)	[2]																																																																																								(13)	[2]		(9)	[2]																																																																(6)	[2]		(6)	[2]																																																																								(5)	[2]		(6)	[2]
POR net receivables	206			170																																																																																									74			46																																																																	64			59																																																																									68			65
Energy Infrastructure Modernization Act [Abstract]
Current length of state legislation enacted			10 years
Increased revenue requirement																																																																																													359
Expected revenue adjustment for prior year																																																																																													194
Expected revenue adjustment for current year																																																																																													165
Excess basis points over treasury after year one																																																																																													5.80%
Senate Bill [Abstract]
Next 6 months Projected Revenue																																																																																													15
Year 2 Projected Revenue	65
Next 12 months Projected CapEx	40
Year 2 Projected CapEx	45
Next 6 months estimated refund																																																																																													14
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																																																																																																																																									101
Adjustment to Requested increase in electric revenues																																																																																																343
Recovery request for Operating and Maintenance expenses of AMI Pilot Program																																																																																																40
Requested increase in gas revenues																																																																																																																																																																																																																																													30
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																																																																																																																																													81
Increase in gas delivery service revenue resulting from rate case settlement or order.																																																																																																																																																																																																																																													32
Regulatory Assets Transfer Changes																																																																																																																																																																																																																																												6	8
Severance Recovered Through Distribution Rates																																																																																																																																																																																																																																													20
ComEd's proposed increase to net distribution revenue requirement related to uncollectable account expense																																																																																																22
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
Estimated Refund Obligation To Customers																																																																																																			37
Annual Transmission Formula Rate Update [Abstract]
Gross transmission revenue requirement																																																																																													488		450																																																																																																																																														158			156
Transmission revenue true up																																																																																													25		5																																																																																																																																														1			2
Net transmission revenue requirement																																																																																													513		445																																																																																																																																														157			158
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
Spend on smart grid investments																																																																																																																																																																	120
Smart meter spend to date																																																																																																																																																																	312
Smart grid infrastructure spend to date																																																																																																																																																																	107
Total smart grid and smart meter investment grant amount																																																																																																																																																																	200
Smart meter investment grant awarded																																																																																																																																																																	140
Smart grid investment grant awarded																																																																																																																																																																	60																																																																												200
Reimbursements received from the DOE																																																																																																																																																																	167																																																																												176
Outstanding reimbursable DOE Smart Grid Investment Grant expenditures																																																																																																																																																																	10																																																																												17
Regulatory assets for original smart meters purchased																																																																																																																																																																	17
Carrying value of originally installed Smart Meters, net of reimbursements from DOE																																																																																																																																																																	19
Amount of reimbursements received from the DOE applied to the originally installed Smart Meters.																																																																																																																																																																	16
Total Projected smart meter smart grid spend																																																																																																																																																																																																																																													480
New Electric Generation [Abstract]
Megawatt capacity of new generating plant																																																																																																																																																																																																																																													700
Energy Efficiency Program [Abstract]
Cumulative Consumption Reduction Targets																																																																																																																																																																																																																																										2.90%
Amount of cost recoveries sought under the Direct Load Control Program.																																																																																																																																																																																																																																											12
Proposed funding of estimated costs associated with DLC demand program due to modification of incentive levels for other Phase II programs.																																																																																																																																																																																																																																											10
Advanced metering infrastructure pilot program [Abstract]
Collections Under Rider Amp																																																																																																24
Authorized Return On Rate Base [Abstract]
Weighted Average Debt And Equity Return Electric Distribution																																																																																																0.0691%		0.0701%
Weighted Average Debt And Equity Return																																																																																													8.70%		8.91%																																																																																																																																														8.35%		8.43%
Rate Of Return On Common Equity																																																																																													11.50%			0.0872%		0.0872%																																																																																																																																											10.80%			11.30%
Rate Of Return On Common Equity in FERC Complaint																																																																																																																																																																																																																																													8.70%
Potential refund resulting from the FERC Comlaint																																																																																																																																																																																																																																													10
Common Equity Component Cap																																																																																													55.00%
Regulatory Assets And Liabilities Other Disclosures [Abstract]
Over under recovered transmission costs																																																																																																																																																																	7
Over under recovered electric supply costs																																																																																																																																																																	35			47
Over under recovered gas supply costs																																																																																																																																																																	24			1
Amortization of rate stabilization deferral	29		15																																																																																																																																																																																																																																										29		25
Recovered portion of regulatory assets	112		56																																																																																						0				62		38																																																																		4		5																																																																										47		27
Regulatory Asset [Line Items]
Noncurrent regulatory assets	6,519			6,497																												3,622	[3]	3,673	[3]	1,409	1,382	99	70	17	17	245	191	63	68	233	[4]	256	[4]	6	[5]	12	[5]	14	28	93	90	215	232	1	2	0			0	69	49	0		3	1	3	2	4	6	37	40	194	225	152	126			0	10	[6]	32	25			0		732			666																					0	[3]	64	62	22	10	0	245	191	58	62	0	[4]	0	[5]	0	0	12	68	65	184	197	1	2	0	0	0		69	49	0		0	0	0	0	0	0	0	0	0		21	16	1,400			1,378																						0	[3]	0	[3]	1,279	1,255	32	29	17	17	0	5	6	0	[4]	0	[5]		0	0	25	25	30	33	0	0		0	0	0	0		3	3	1	2	0	0	0	0	0	0	0	0	0		8	8				536			522																							0	[3]	0	[3]	66	65	45	31	0	0	0	9	9	0	[4]	0	[5]	14	16	0	1	2	0	0	0	0	0	0	0				0	0	0	0	4	6	37	40	194	225	152	126			0	10	[6]	4	2
Current regulatory assets	804			764																												308	[3]	304	[3]	14	14	4	3			84	18	12	14	0	[4]	0		46	[5]	77	[5]	29	29	0	0	49	58	2	3	3	11	0	0	16	18	71	43	0	2	1	1	3	3	13	16	68	67	42	56	5	[7]		1	[6]	37	23					274			388																					0	[3]	5	5	4	3	0	84	18	9	11	0	[4]	0	[5]	0	25	25	0	0	42	51	2	3	0	0	0	226	16	18	71	14	0	0	0	0	0		0	0	0	0	16	14	35			32																						0	[3]			0		0		0		0	3	3	0	[4]	0	[5]	0	0	0	0	0	6	6	0	3	11	0	0	0	1	[8]	0	1	2	1	0	0	0	0	0	0	0	0	0	0	21	9				142			190																							0	[3]			9	9	0	0	0	0	0	1	1	0	[4]	0	[5]	4	4	0	1	1	0	0	0	0	0	0	28	[9]	9	19	0	0	0	0	3	3	13	16	68	67	42	56	5	[7]	5	1	[6]	0	0		0
Net regulatory asset																																																																																																																												329	209
Regulatory Liabilities [Line Items]
Regulatory Liability Current	357			368			0	99	97	98	131	20	20	6	78	54	3	3	2	40	[10]	40	[10]	8	[7]	7	[7]	8	2	1																																																															151			170						0	78	75	31	43	0	6	2	6	0	0	40	[10]	40	[10]																																													166			169			0	0	67	88	20	20	0	66	[11]	48	[11]	3	3	2	8	8	1	1																																																					40			29		0	21	22	0	0	0	10	[9]	0	7	0	0	8	[7]	7	[7]	1	9	7	1	3																																																				8
Noncurrent regulatory liabilities	$ 4,044			$ 3,981		$ 2,434	$ 2,397	$ 1,422	$ 1,406		$ 0	$ 121	$ 132	$ 0	$ 4	$ 0		$ 0	$ 0									$ 46	$ 3	$ 11	$ 7																																																											$ 3			$ 3,276			$ 3,229					$ 2,068	$ 2,037	$ 1,201	$ 1,192	$ 0	$ 0	$ 0	$ 0	$ 4	$ 0	$ 0	$ 0																																																	$ 547			$ 538		$ 366	$ 360	$ 0		$ 0	$ 121	$ 132	$ 0			$ 0			$ 0	$ 0	$ 42	$ 46		$ 11	$ 7																																																				$ 221			$ 214		$ 0	$ 221	$ 214	$ 0	$ 0	$ 0			$ 0		$ 0	$ 0																																																													$ 42

[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] Pension and other postretirement benefit regulatory assets include a regulatory asset established at the date of the merger related to BGE's portion of the deferred costs associated with legacy Constellation’s pension and other postretirement benefit plans. That BGE-related regulatory asset is being amortized over a period of approximately 12 years, which generally represents the expected average remaining service period of plan participants at the date of the merger

[4] 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 11 – Debt and Credit Agreements for additional information.

[5] 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.

[6] ReIates to integration costs to achieve distribution synergies related to the merger transaction.

[7] Represents the electric and gas distribution costs recoverable from or refundable to customers under BGE’s decoupling mechanism. As of June 30, 2013, includes $1 million of under-recovered electric distribution costs and $9 million of over-recovered gas distribution costs under BGE’s decoupling mechanism. As of December 31, 2012, relates to $5 million of under-recovered electric distribution costs and $7 million of over-recovered gas distribution costs under BGE’s decoupling mechanism.

[8] Relates to under-recovered transmission costs.

[9] Relates to $7 million of over-recovered natural gas supply costs and to $3 million of over-recovered natural electric supply costs as of June 30, 2013. As of December 31, 2012, includes to $9 million of under-recovered electric supply costs and $19 million of under-recovered natural gas supply costs.

[10] 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 of Exelon’s 2012 Form 10-K for additional information regarding the 2007 Rate Case.

[11] Includes $35 million related to the over-recovered electric supply costs under the GSA, $24 million related to the over-recovered natural gas costs under the PGC and $7 million related to over-recovered electric transmission costs as of June 30, 2013. As of December 31, 2012, includes $47 million related to the over-recovered electric supply costs under the GSA and $1 million related to the over-recovered natural gas costs under the PGC.