Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Current		$ 785	$ 847
Noncurrent		5,976	6,076
Regulatory Assets		6,761	6,923
Business Combination, Integration Related Costs		89
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,193	3,256
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,574	1,542
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		349	296
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		275	371
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		51	57
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		177	190
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11	12
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	116
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		245	257
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		50	67
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		223	207
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		53	48
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25	30
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	160
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236	248
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7	8
ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	2
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		46	46
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		276	349
Noncurrent		834	852
Regulatory Assets		1,110	1,201
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		65	64
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		119	91
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[1]	275	371
UnderOverRecoveredDistributionServiceCosts		209	286
CostRecoveryForSignificantOneTimeEvents		66	85
RegulatoryAssetsDueToDeferredStormCosts		51	66
Business Combination, Integration Related Costs		15	19
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		49	53
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		76	74
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		210	219
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		50	67
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		223	207
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	34	33
Business Combination, Integration Related Costs		7	7
ElectricTransmissionCostsUnderRecovery		26	22
Underrecovered Electric Supply cost		1	4
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9	22
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		42	29
Noncurrent		1,552	1,529
Regulatory Assets		1,594	1,558
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,432	1,400
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		70	77
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	4
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		26	26
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34	37
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30	14
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		207	214
Noncurrent		486	510
Regulatory Assets		693	724
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		77	78
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		160	128
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8	9
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11	12
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19	16
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	19	15
Business Combination, Integration Related Costs		4	4
Underrecovered Electric Supply cost		18	10
Environmental Restoration Costs		1	1
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25	30
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	160
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236	248
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7	8
Baltimore Gas and Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	2
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5	7
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
UnderRecoveredElectricRevenueDecoupling			$ 7
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Underrecovered Electric Supply cost		$ 6

[1] As of June 30, 2015, ComEd’s regulatory asset of $275 million was comprised of $209 million for the applicable annual reconciliations and $66 million related to significant one-time events including $51 million of deferred storm costs and $15 million of Constellation merger and integration related costs. As of December 31, 2014, ComEd’s regulatory asset of $371 million was comprised of $286 million for the applicable annual reconciliations and $85 million related to significant one-time events, including $66 million of deferred storm costs and $19 million of Constellation merger and integration related costs. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for further information.

[2] As of June 30, 2015, ComEd’s regulatory asset of $34 million included $1 million related to under-recovered energy costs for non-hourly customers, $26 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2015, ComEd’s regulatory liability of $30 million included $10 million related to over-recovered energy costs for hourly customers and $20 million associated with revenues received for renewable energy requirements. As of December 31, 2014, ComEd’s regulatory asset of $33 million included $4 million related to under-recovered energy costs for non-hourly customers, $22 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2014, ComEd’s regulatory liability of $19 million included $3 million related to over-recovered energy costs for hourly customers and $16 million associated with revenues received for renewable energy requirements.

[3] As of June 30, 2015, BGE's regulatory asset of $19 million included $1 million associated with transmission costs recoverable through its FERC approved formula rate and $18 million related to under-recovered electric energy costs. As of June 30, 2015, BGE's regulatory liability of $19 million related to $18 million of over-recovered natural gas supply costs and $6 million of over-recovered energy costs, offset by $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory asset of $15 million included $10 million related to under-recovered electric energy costs, $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory liability of $7 million related to over-recovered natural gas supply costs.