Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 4,570	$ 4,860
Regulatory liabilities	369	310
Noncurrent regulatory liabilities	4,201	4,550
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	94	88
Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,577	2,879
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,527	1,566
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	92	59
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	9	10
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	95	102
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	28	49
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	131	84
Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1	12
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	16	8
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3,614	3,780
Regulatory liabilities	155	125
Noncurrent regulatory liabilities	3,459	3,655
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,172	2,389
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,332	1,343
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	52	25
Commonwealth Edison Co [Member] | Dlc Program Cost [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]
Renewable Energy Requirement Revenue	24	16
Regulatory Liabilities	53	19
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	5	1
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	639	747
Regulatory liabilities	112	90
Noncurrent regulatory liabilities	527	657
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
PECO Energy Co [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	405	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	40	34
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	9	10
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	95	102
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	28	49
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	60	58
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	4
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	222	244
Regulatory liabilities	38	44
Noncurrent regulatory liabilities	184	200
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	195	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] | 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	18	7
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	1	12
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 8	2
Over Recovered Electric Energy And Transmission Costs [Member] | Commonwealth Edison Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 19