Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Current		$ 409	$ 310
Noncurrent		4,462	4,550
Regulatory Liabilities		4,871	4,860
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		68	88
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,831	2,879
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,563	1,566
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41	27
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9	10
Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38	32
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		102	102
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		33	49
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		134	84
Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	2
Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			3
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		40	12
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10	6
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Current		91	44
Noncurrent		185	200
Regulatory Liabilities		276	244
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		212	223
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	19	7
Over recovered Natural Gas Supply Cost		18	7
Underrecovered Electric Supply cost		6
Baltimore Gas and Electric Company [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			0
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	40	12
Over Recovered Electric Revenue Decoupling		11
Over Recovered Natural Gas Revenue Decoupling		29	12
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5	2
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Current		117	90
Noncurrent		633	657
Regulatory Liabilities		750	747
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		477	490
PECO Energy Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	2
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9	10
PECO Energy Co [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38	32
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		102	102
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		33	49
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	85	58
Over recovered Natural Gas Supply Cost		44	3
Default Service Provider Program Costs		35	39
Over Recovered Electric Transmission Costs		5	16
Non Bypassable Service Charges		1
PECO Energy Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	2
PECO Energy Co [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			0
PECO Energy Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	2
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Current		154	125
Noncurrent		3,622	3,655
Regulatory Liabilities		3,776	3,780
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,354	2,389
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,351	1,343
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		39	25
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[4]	30	19
Over Recovered electric Supply Costs		10	3
Renewable Energy Requirement Revenue		20	16
Commonwealth Edison Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			3
Commonwealth Edison Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	1
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost		18	10
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost		$ 1	$ 4

[1] 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.

[2] Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of June 30, 2015, BGE had a regulatory liability of $11 million related to over-recovered electric revenue decoupling and a regulatory liability of $29 million related to over-recovered natural gas revenue decoupling. As of December 31, 2014, BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $12 million related to over-recovered natural gas revenue decoupling.

[3] ncluded $35 million related to the DSP program, $44 million related to the over-recovered natural gas costs under the PGC, $5 million related to over-recovered electric transmission costs and $1 million related to the Non-Bypassable service charge included in the DSP program. As of December 31, 2014, PECO's regulatory liability of $58 million included $39 million related to the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs.

[4] 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.