Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Regulatory Assets	$ 6,872	$ 6,923
Current	421	310
Noncurrent	4,566	4,550
Regulatory Liabilities	4,987	4,860
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	72	88
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,920	2,879
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,567	1,566
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	27	27
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	10	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	106	102
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	34	49
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	142	84
Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3	2
Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3	3
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	56	12
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	9	6
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	678	724
Current	124	44
Noncurrent	187	200
Regulatory Liabilities	311	244
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	37	12
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Electric Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	19
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	216	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	35	7
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	0
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	56	12
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	4	2
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	31	7
Baltimore Gas and Electric Company [Member] | Over Recovered Electric Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	4	10
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	1,584	1,558
Current	119	90
Noncurrent	662	657
Regulatory Liabilities	781	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	500	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	10	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	106	102
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	34	49
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	84	58
PECO Energy Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3	2
PECO Energy Co [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	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	4	2
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	1,183	1,201
Current	131	125
Noncurrent	3,692	3,655
Regulatory Liabilities	3,823	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	2,420	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	25	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	23	19
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	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	1	1
Under Recovered Distribution Service Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	316	371
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	0	0
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	0	0
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	316	371
Under Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	41	48
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	4	15
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	0	0
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	37	33
Under-Recovered Electric Revenue Decoupling [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		$ 7