Regulatory Matters (Details) (USD $)																																																																				1 Months Ended	9 Months Ended																																																																				9 Months Ended						0 Months Ended	9 Months Ended																																																																								0 Months Ended	9 Months Ended							0 Months Ended	9 Months Ended																																																																				9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011		Sep. 30, 2012 Nuclear Decommissioning [Member]	Dec. 31, 2011 Nuclear Decommissioning [Member]	Sep. 30, 2012 Removal Costs [Member]	Dec. 31, 2011 Removal Costs [Member]	Sep. 30, 2012 Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2011 Energy Efficiency Demand Response Programs [Member]	Sep. 30, 2012 Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2011 Electric Transmission And Distribution Tax Repairs [Member]	Sep. 30, 2012 Over Recovered Distribution Services Costs [Member]	Sep. 30, 2012 Over Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2011 Over Recovered Uncollectible Accounts Expense [Member]	Sep. 30, 2012 Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Over Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2011 Over-Recovered Universal Service Fund Costs [Member]	Sep. 30, 2012 Over-Recovered AEPS Costs [Member]	Dec. 31, 2011 Over-Recovered AEPS Costs [Member]	Sep. 30, 2012 Customer Rate Credit [Member]	Sep. 30, 2012 Regulatory Liabilities Other [Member]	Sep. 30, 2012 Pension and Other Postretirement Benefits [Member]		Dec. 31, 2011 Pension and Other Postretirement Benefits [Member]	Sep. 30, 2012 Deferred Income Taxes [Member]	Dec. 31, 2011 Deferred Income Taxes [Member]	Sep. 30, 2012 AMI Expenses [Member]	Dec. 31, 2011 AMI Expenses [Member]	Sep. 30, 2012 Under Recovered Distribution Service Costs [Member]	Dec. 31, 2011 Under Recovered Distribution Service Costs [Member]	Sep. 30, 2012 Debt Costs [Member]	Dec. 31, 2011 Debt Costs [Member]	Sep. 30, 2012 Fair Value Of Long Term Debt [Member]		Sep. 30, 2012 Fair Value Of Supply Contract [Member]		Sep. 30, 2012 Severance [Member]	Dec. 31, 2011 Severance [Member]	Sep. 30, 2012 Asset Retirement Obligations [Member]	Dec. 31, 2011 Asset Retirement Obligations [Member]	Sep. 30, 2012 MGP Remediation Costs [Member]	Dec. 31, 2011 MGP Remediation Costs [Member]	Sep. 30, 2012 RTO Startup Costs [Member]	Dec. 31, 2011 RTO Startup Costs [Member]	Sep. 30, 2012 Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2011 Under Recovered Universal Service Fund Costs Member [Member]	Sep. 30, 2012 Financial Swap with Generation [Member]	Dec. 31, 2011 Financial Swap with Generation [Member]	Sep. 30, 2012 Renewable Energy And Associated REC [Member]	Dec. 31, 2011 Renewable Energy And Associated REC [Member]	Sep. 30, 2012 Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Under Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 DSP Program Electric Procurement Contracts [Member]	Sep. 30, 2012 DSP II Program Electric Procurement Contracts [Member]	Dec. 31, 2011 DSP Program costs [Member]	Sep. 30, 2012 Deferred Storm Costs [Member]	Dec. 31, 2011 Deferred Storm Costs [Member]	Sep. 30, 2012 Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2011 Electric Generation Related Regulatory Asset [Member]	Sep. 30, 2012 Rate Stabilization Deferral [Member]	Dec. 31, 2011 Rate Stabilization Deferral [Member]	Sep. 30, 2012 Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2011 Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 Other Regulatory Assets [Member]	Dec. 31, 2011 Other Regulatory Assets [Member]	Sep. 30, 2008 Commonwealth Edison Co [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Years		Sep. 30, 2011 Commonwealth Edison Co [Member]	Feb. 29, 2012 Commonwealth Edison Co [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member]		Sep. 30, 2012 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Nuclear Decommissioning [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Removal Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Removal Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Energy Efficiency Demand Response Programs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Over Recovered Distribution Services Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Over Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Over-Recovered AEPS Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Over-Recovered AEPS Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Customer Rate Credit [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Pension and Other Postretirement Benefits [Member]		Dec. 31, 2011 Commonwealth Edison Co [Member] Pension and Other Postretirement Benefits [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Deferred Income Taxes [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] AMI Expenses [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] AMI Expenses [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Under Recovered Distribution Service Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Debt Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Debt Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Fair Value Of Long Term Debt [Member]		Sep. 30, 2012 Commonwealth Edison Co [Member] Fair Value Of Supply Contract [Member]		Sep. 30, 2012 Commonwealth Edison Co [Member] Severance [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Severance [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Asset Retirement Obligations [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] MGP Remediation Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] RTO Startup Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Financial Swap with Generation [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Financial Swap with Generation [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Renewable Energy And Associated REC [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Under Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] DSP Program Electric Procurement Contracts [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] DSP Program Electric Procurement Contracts [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] DSP II Program Electric Procurement Contracts [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Deferred Storm Costs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Deferred Storm Costs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Electric Generation Related Regulatory Asset [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Rate Stabilization Deferral [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] Other Regulatory Assets [Member]	Dec. 31, 2011 Commonwealth Edison Co [Member] Other Regulatory Assets [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] One Year From Balance Sheet Date [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Sep. 30, 2012 Commonwealth Edison Co [Member] More Than Five Years From Balance Sheet Date And Thereafter [Member]	Jun. 01, 2013 PECO Energy Co [Member]	Sep. 30, 2012 PECO Energy Co [Member] SmartMeters		Dec. 31, 2011 PECO Energy Co [Member]		Sep. 30, 2012 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Dec. 31, 2011 PECO Energy Co [Member] Nuclear Decommissioning [Member]	Sep. 30, 2012 PECO Energy Co [Member] Removal Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Removal Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Energy Efficiency Demand Response Programs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Electric Transmission And Distribution Tax Repairs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Over Recovered Distribution Services Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2011 PECO Energy Co [Member] Over Recovered Uncollectible Accounts Expense [Member]	Sep. 30, 2012 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Dec. 31, 2011 PECO Energy Co [Member] Over Recovered Energy And Transmission Costs [Member]		Sep. 30, 2012 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Over-Recovered Universal Service Fund Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Over-Recovered AEPS Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Over-Recovered AEPS Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Customer Rate Credit [Member]	Sep. 30, 2012 PECO Energy Co [Member] Regulatory Liabilities Other [Member]	Sep. 30, 2012 PECO Energy Co [Member] Gas Distribution Tax Repairs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Pension and Other Postretirement Benefits [Member]		Dec. 31, 2011 PECO Energy Co [Member] Pension and Other Postretirement Benefits [Member]	Sep. 30, 2012 PECO Energy Co [Member] Deferred Income Taxes [Member]	Dec. 31, 2011 PECO Energy Co [Member] Deferred Income Taxes [Member]	Sep. 30, 2012 PECO Energy Co [Member] AMI Expenses [Member]	Dec. 31, 2011 PECO Energy Co [Member] AMI Expenses [Member]	Sep. 30, 2012 PECO Energy Co [Member] Under Recovered Distribution Service Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Under Recovered Distribution Service Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Debt Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Debt Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Fair Value Of Long Term Debt [Member]		Sep. 30, 2012 PECO Energy Co [Member] Fair Value Of Supply Contract [Member]		Sep. 30, 2012 PECO Energy Co [Member] Severance [Member]	Dec. 31, 2011 PECO Energy Co [Member] Severance [Member]	Sep. 30, 2012 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Dec. 31, 2011 PECO Energy Co [Member] Asset Retirement Obligations [Member]	Sep. 30, 2012 PECO Energy Co [Member] MGP Remediation Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] MGP Remediation Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] RTO Startup Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] RTO Startup Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2011 PECO Energy Co [Member] Under Recovered Universal Service Fund Costs Member [Member]	Sep. 30, 2012 PECO Energy Co [Member] Financial Swap with Generation [Member]	Dec. 31, 2011 PECO Energy Co [Member] Financial Swap with Generation [Member]	Sep. 30, 2012 PECO Energy Co [Member] Renewable Energy And Associated REC [Member]	Dec. 31, 2011 PECO Energy Co [Member] Renewable Energy And Associated REC [Member]	Sep. 30, 2012 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]		Dec. 31, 2011 PECO Energy Co [Member] Under Recovered Energy And Transmission Costs [Member]		Sep. 30, 2012 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]	Dec. 31, 2011 PECO Energy Co [Member] DSP Program Electric Procurement Contracts [Member]	Sep. 30, 2012 PECO Energy Co [Member] DSP II Program Electric Procurement Contracts [Member]	Sep. 30, 2012 PECO Energy Co [Member] Deferred Storm Costs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Deferred Storm Costs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2011 PECO Energy Co [Member] Electric Generation Related Regulatory Asset [Member]	Sep. 30, 2012 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2011 PECO Energy Co [Member] Rate Stabilization Deferral [Member]	Sep. 30, 2012 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2011 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Other Regulatory Assets [Member]	Dec. 31, 2011 PECO Energy Co [Member] Other Regulatory Assets [Member]	Jun. 01, 2013 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 PECO Energy Co [Member] Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 PECO Energy Co [Member] One Year From Balance Sheet Date [Member]	Sep. 30, 2012 PECO Energy Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Sep. 30, 2012 PECO Energy Co [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Sep. 30, 2012 PECO Energy Co [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Sep. 30, 2012 PECO Energy Co [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Sep. 30, 2012 PECO Energy Co [Member] More Than Five Years From Balance Sheet Date And Thereafter [Member]	Jul. 27, 2012 Baltimore Gas and Electric Company [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] SmartMeters		Sep. 30, 2011 Baltimore Gas and Electric Company [Member]	Jun. 01, 2015 Baltimore Gas and Electric Company [Member] MW	Dec. 31, 2011 Baltimore Gas and Electric Company [Member]		Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Nuclear Decommissioning [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Nuclear Decommissioning [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Removal Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Energy Efficiency Demand Response Programs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Energy Efficiency Demand Response Programs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution Tax Repairs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Electric Transmission And Distribution Tax Repairs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Distribution Services Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Uncollectible Accounts Expense [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Over Recovered Uncollectible Accounts Expense [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Over Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Over-Recovered Universal Service Fund Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Over-Recovered Universal Service Fund Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Over-Recovered AEPS Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Over-Recovered AEPS Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Customer Rate Credit [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Pension and Other Postretirement Benefits [Member]		Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Pension and Other Postretirement Benefits [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Deferred Income Taxes [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] AMI Expenses [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Distribution Service Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Under Recovered Distribution Service Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Debt Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Fair Value Of Long Term Debt [Member]		Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Fair Value Of Supply Contract [Member]		Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Severance [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Severance [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Asset Retirement Obligations [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Asset Retirement Obligations [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] MGP Remediation Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] RTO Startup Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] RTO Startup Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Universal Service Fund Costs Member [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Under Recovered Universal Service Fund Costs Member [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Financial Swap with Generation [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Financial Swap with Generation [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Renewable Energy And Associated REC [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Renewable Energy And Associated REC [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Under Recovered Energy And Transmission Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] DSP Program Electric Procurement Contracts [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] DSP Program Electric Procurement Contracts [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] DSP II Program Electric Procurement Contracts [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Deferred Storm Costs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Electric Generation Related Regulatory Asset [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Rate Stabilization Deferral [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Energy Efficiency And Demand Response Programs [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] Other Regulatory Assets [Member]	Dec. 31, 2011 Baltimore Gas and Electric Company [Member] Other Regulatory Assets [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] One Year From Balance Sheet Date [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Sep. 30, 2012 Baltimore Gas and Electric Company [Member] More Than Five Years From Balance Sheet Date And Thereafter [Member]	Sep. 30, 2012 Exelon Corporate [Member] Gas Distribution Tax Repairs [Member]
Purchase Of Receivables [Abstract]
POR gross receivables	$ 203,000,000	[1]	$ 68,000,000	[1]																																																																	$ 56,000,000	[1]			$ 16,000,000	[1]																																																																						$ 72,000,000	[1]	$ 52,000,000	[1]																																																																														$ 75,000,000	[1]			$ 61,000,000	[1]
POR Allowance for uncollectible accounts	(18,000,000)	[2]	(5,000,000)	[2]																																																																	(6,000,000)	[2]			0	[2]																																																																						(7,000,000)	[2]	(5,000,000)	[2]																																																																														(5,000,000)	[2]			(3,000,000)	[2]
POR net receivables	185,000,000		63,000,000																																																																		50,000,000				16,000,000																																																																							65,000,000		47,000,000																																																																															70,000,000				58,000,000
Discount on purchased receivables																																																																																																																																																1.00%
Energy Infrastructure Modernization Act [Abstract]
Additional investment to modernize system and implement smart grid technology.																																																																					2,600,000,000
Annual contribution to fund customer assistance programs																																																																					10,000,000
Contribution to a science and technology innovation trust																																																																					15,000,000
Subsequent annual contributions to the trust																																																																					4,000,000
Time period for AMI Deployment																																																																					10
Planned capital spend by a utility under state enacted legislation																																																																					233,000,000
Annual revenue requirement reduction																																																																					168,000,000
Annual revenue requirement reduction incremental to proposal																																																																					110,000,000
Annual revenue requirement incremental reduction attributable to alternative recovery																																																																					50,000,000
Annual revenue requirement incremental reduction attributable to pensions																																																																					35,000,000
Annual revenue requirement incremental reduction attributable to incentives																																																																					10,000,000
Annual revenue requirement incremental reduction attributable to other adjustments																																																																					15,000,000
Regulatory asset reduction due to final order																																																																					100,000,000
Deferral of AMI plan																																																																					50,000,000
Deferral of additional capital investment																																																																					15,000,000
Expected revenue adjustment in subsequent quarter																																																																					135,000,000
Distribution Rate Case [Abstract]
Requested increase in electric revenues																																																																																																																																																																																																																																131,000,000
Requested increase in gas revenues																																																																																																																																																																																																																																45,000,000
Requested rate of return on common equity																																																																																																																																																																																																																																10.50%
Rate of return on common equity electric distribution																																																																				10.30%
Intervenor potential refund submitted in testimony																																																																								37,000,000
Increase in gas delivery service revenue resulting from rate case settlement																																																																																																																																																20,000,000
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
Annual Transmission Formula Rate Update [Abstract]
Gross transmission revenue requirement																																																																					450,000,000		438,000,000
Transmission revenue true up																																																																					5,000,000		16,000,000
Net transmission revenue requirement																																																																					445,000,000		422,000,000
PJM Transmission Rate Design And Operating Agreements Abstract
RTEP construction commitments																																																																					124,000,000																																																																				8,000,000	57,000,000	9,000,000	20,000,000	25,000,000	5,000,000		86,000,000																																																																										6,000,000	9,000,000	11,000,000	13,000,000	21,000,000	26,000,000		165,000,000																																																																				(32,000,000)	(20,000,000)	44,000,000	115,000,000	52,000,000	6,000,000
Smart Meter and Smart Grid Investments [Abstract]
Estimated number of smart meters to be installed																																																																																																																																																																																																																																	2,000,000
Expected number of smart meters to be deployed during the first phase of Smart Meter Installment Plan																																																																																																																																																600,000
Estimated Cost related to first phase deployment of Smart Meter Procurement and Installation Plan																																																																																																																																																415,000,000
Smart grid investment grant amount																																																																																																																																																200,000,000																																																																																	200,000,000
Amount of Smart grid investment grant utilized during the first phase deployment																																																																																																																																																140,000,000
Number of previously installed smart meters to be replaced																																																																																																																																																186,000
Outstanding reimbursable DOE Smart Grid Investment Grant expenditures																																																																																																																																																16,000,000																																																																																	13,000,000
Reimbursements received from the DOE																																																																																																																																																130,000,000																																																																																	126,000,000
Carrying value of originally installed Smart Meters, net of reimbursements from DOE																																																																																																																																																18,000,000
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
New Electric Generation [Abstract]
Megawatt capacity of new generating plant																																																																																																																																																																																																																																				700
Energy Efficiency Program [Abstract]
Maximum civil penalty under Act 129																																																																																																																																																																																																																								20,000,000
Cumulative Consumption Reduction Targets																																																																																																																																															2.90%																																																																									2.90%
Consumption reduction target (as a percentage) mandated by the Energy Efficiency Program - Phase II Implemtation Order for programs directed towards the Utility's low income sector.																																																																																																																																																																																																																								4.50%
Consumption reduction targets for public sector under Act 129 Phase II Implementation Order																																																																																																																																																																																																																								10.00%
Total approved amount under phase II of Act 129 as percent of total annual revenue																																																																																																																																																																																																																									2.00%
Advanced metering infrastructure pilot program [Abstract]
Collections Under Rider Amp																																																																									24,000,000
Natural Gas Distribution Rate Case [Abstract]
Gas Distribution Tax Repairs Refund																																																																																																																																																54,000,000
Authorized Return On Rate Base [Abstract]
Weighted Average Debt And Equity Return																																																																					8.91%		9.10%
Rate Of Return On Common Equity																																																																					11.50%
Common Equity Component Cap																																																																					55.00%
Natural Gas Supplier Tariff [Abstract]
Natural gas supplier tariff total collateral																																																																																																																																																14,000,000
Maryland Electric And Natural Gas Distribution Rate Cases [Abstract]
Deferral of total costs																																																																																																																																																																																																																																			19,000,000
Deferral of storm costs																																																																																																																																																																																																																																			16,000,000
Regulatory Asset [Line Items]
Noncurrent regulatory assets	6,192,000,000		4,518,000,000																					3,499,000,000	[3]	2,794,000,000	1,346,000,000	1,176,000,000	54,000,000	28,000,000	119,000,000	70,000,000	71,000,000	81,000,000	226,000,000	[4]	31,000,000	[5]	36,000,000	38,000,000	84,000,000	74,000,000	227,000,000	129,000,000	3,000,000	4,000,000	0	0	0	0	53,000,000	97,000,000	0	0	2,000,000	2,000,000	2,000,000	7,000,000	0	44,000,000	0	244,000,000	0	117,000,000	0	27,000,000	25,000,000		589,000,000				699,000,000																				0	[3]	0	62,000,000	66,000,000	5,000,000	6,000,000	119,000,000	70,000,000	65,000,000	73,000,000	0	[4]	0	[5]	19,000,000	38,000,000	59,000,000	50,000,000	190,000,000	91,000,000	3,000,000	4,000,000	0	0	0	191,000,000	53,000,000	97,000,000	0	0	0	0	0	0	0	0	0	0	0	0	0	14,000,000	13,000,000								1,323,000,000		1,216,000,000																								0	[3]	0	1,220,000,000	1,110,000,000	24,000,000	22,000,000	0	0	6,000,000	8,000,000	0	[4]	0	[5]	0	0	25,000,000	24,000,000	35,000,000	38,000,000	0	0	0	0	0	0	0	0	0		0		2,000,000	2,000,000	2,000,000	0	0	0	0	0	0	0	0	9,000,000	12,000,000										534,000,000				550,000,000																				0	[3]	0	64,000,000	64,000,000	25,000,000	15,000,000	0	0	9,000,000	10,000,000	0	[4]	0	[5]	17,000,000	1,000,000	0	0	2,000,000	2,000,000	0	0	0	0	0	0	0	0	0	0	0	0	0	7,000,000	9,000,000	44,000,000	56,000,000	244,000,000	295,000,000	117,000,000	95,000,000	5,000,000	3,000,000
Current regulatory assets	786,000,000		390,000,000																					264,000,000	[3]	204,000,000	13,000,000	5,000,000	2,000,000	2,000,000	0	14,000,000	14,000,000	18,000,000	43,000,000	[4]	94,000,000	[5]	30,000,000	25,000,000	0	0	65,000,000	30,000,000	3,000,000	3,000,000	8,000,000	3,000,000	0	0	17,000,000	9,000,000	62,000,000	57,000,000	2,000,000	0	3,000,000	3,000,000	0	16,000,000	0	65,000,000	0	55,000,000	0	30,000,000	17,000,000		511,000,000				657,000,000																				0	[3]	0	5,000,000	5,000,000	2,000,000	2,000,000	0	14,000,000	11,000,000	15,000,000	0	[4]	0	[5]	25,000,000	25,000,000	0	0	58,000,000	24,000,000	3,000,000	3,000,000	0	0	352,000,000	503,000,000	17,000,000	9,000,000	22,000,000	48,000,000	0	0	0	0	0	0	0	0	0	0	0	16,000,000	9,000,000								42,000,000		39,000,000																								2,000,000	[3]	7,000,000	0	0	0	0	0	0	3,000,000	3,000,000	0	[4]	0	[5]	0	0	0	0	6,000,000	6,000,000	0	0	8,000,000	3,000,000	0	0	0	0	7,000,000	[6]	9,000,000	[6]	2,000,000	3,000,000	0	0	0	0	0	0	0	0	0	14,000,000	8,000,000										189,000,000				174,000,000																				1,000,000	[3]	3,000,000	8,000,000	7,000,000	0	0	0	0	2,000,000	2,000,000	0	[4]	0	[5]	5,000,000	0	0	0	1,000,000	1,000,000	0	0	0	0	0	0	0	0	33,000,000	50,000,000	0	0	0	3,000,000	3,000,000	16,000,000	16,000,000	65,000,000	63,000,000	55,000,000	29,000,000	0	0
Net regulatory asset																																																																																																				74,000,000	84,000,000
Regulatory Liabilities [Line Items]
Regulatory Liability Current	299,000,000		197,000,000		0	0	94,000,000	61,000,000	82,000,000	49,000,000	18,000,000	19,000,000	45,000,000	10,000,000	15,000,000	39,000,000	42,000,000	3,000,000	3,000,000	1,000,000	8,000,000	1,000,000	1,000,000																																														172,000,000				137,000,000		0	0	73,000,000	61,000,000	37,000,000	49,000,000	0	0	45,000,000	10,000,000	15,000,000	7,000,000	12,000,000	0	0	0	0	0																																																				105,000,000		60,000,000		0	0	0	0	45,000,000	0	18,000,000	19,000,000	0	0	0	32,000,000	[7]	30,000,000	[7]	3,000,000	3,000,000	1,000,000	8,000,000	0	1,000,000	5,000,000																																																								22,000,000				18,000,000		0	0	21,000,000	18,000,000	0	0	0	0	0	0	0	0	0	0	0	0	0	1,000,000																																																			5,000,000
Noncurrent regulatory liabilities	4,000,000,000		3,627,000,000		2,383,000,000	2,222,000,000	1,397,000,000	1,185,000,000	33,000,000	69,000,000	138,000,000	151,000,000	0	0	0	0	0	0	0	0	0	0																																															3,206,000,000				3,042,000,000		2,021,000,000	1,857,000,000	1,185,000,000	1,185,000,000	0	0	0	0	0	0	0	0	0	0	0	0	0	0																																																				582,000,000		585,000,000		362,000,000	365,000,000	0	0	33,000,000	69,000,000	138,000,000	151,000,000	0	0	0	0		0		0	0	0	0	0		49,000,000																																																								212,000,000				200,000,000		0	0	212,000,000	200,000,000	0	0	0	0	0	0	0	0	0	0	0	0	0	0																																																			49,000,000
Regulatory Liabilities Table Footnote Data [Abstract]
Purchased Natural Gas Cost Over-Recovery																																																																																																																																																0		5,000,000
Electric Supply Cost Over-Recovery																																																																																																																																																32,000,000		25,000,000
Electric Transmission Costs Under-Recovery																																																																																																																																																5,000,000
Purchased Natural Gas Costs Under-Recovery																																																																																																																																																$ 2,000,000

[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] As of September 30, 2012, pension and other postretirement benefit regulatory assets include a regulatory asset established at the date of the merger related to the recognition of BGE's share of the underfunded status of the defined benefit postretirement plan as a liability on Exelon's Consolidated Balance Sheets. The regulatory asset is being amortized in accordance with the authoritative guidance for pensions and postretirement benefits over a period of approximately 12 years. BGE is currently recovering these costs through base rates. BGE is not earning a return on the recovery of these costs in base rates.

[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.

[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.

[6] Includes $5 million related to under-recovered electric transmission costs and $2 million related to under-recovered natural gas costs under the PGC as of September 30, 2012. The balance as of December 31, 2011 related to under-recovered electric transmission costs.

[7] Relates to the over-recovered electric supply costs under the GSA as of September 30, 2012. Includes $5 million related to the over-recovered natural gas costs under the PGC and $25 million related to the over-recovered electric supply costs under the GSA as of December 31, 2011.