Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		12 Months Ended		20 Months Ended
	Dec. 17, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015
Regulatory Assets [Line Items]
Current regulatory assets		$ 759	$ 847	$ 759
Noncurrent regulatory assets		6,065	6,076	6,065
Regulatory Assets		6,824	6,923	6,824
Business Combination, Integration Related Costs		80	179	121
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,156	3,256	3,156
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,616	1,542	1,616
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		399	296	399
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		189	371	189
Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		47	57	47
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		162	190	162
Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9	12	9
Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108	116	108
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		286	257	286
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		52	67	52
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		247	207	247
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		84	48	84
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3	2
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		20	30	20
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		87	160	87
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 279	248	279
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		5 years
Regulatory Assets		$ 6	8	6
ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3	2	3
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30	7	30
Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			46
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		35		35
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7		7
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current regulatory assets		218	349	218
Noncurrent regulatory assets		895	852	895
Regulatory Assets		1,113	1,201	1,113
Business Combination, Integration Related Costs		10	4
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets		64	64	64
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		140	91	140
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		189	371	189
Under over recovered distribution service costs		142	286
Cost recovery for significant one-time events		47	85
Regulatory assets due to deferred storm costs		36	66
Business Combination, Integration Related Costs		11	19
Commonwealth Edison Co [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		46	53	46
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		67	74	67
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		255	219	255
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		52	67	52
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		247	207	247
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		43	33	43
Electric Transmission Costs Under-Recovery		31	22
Business Combination, Integration Related Costs		7	7
Underrecovered Electric Supply cost			4
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		10
Commonwealth Edison Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33
Commonwealth Edison Company [Member] | Under-Recovered Electric Supply Costs [Member]
Regulatory Assets [Line Items]
Electric Transmission Costs Under-Recovery		5
Commonwealth Edison Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
Commonwealth Edison Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current regulatory assets		34	29	34
Noncurrent regulatory assets		1,583	1,529	1,583
Regulatory Assets		1,617	1,558	1,617
Cost recovery for significant one-time events	$ 7
Business Combination, Integration Related Costs		5	2
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 1,473	1,400	1,473
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		10 years
Regulatory Assets		$ 63	77	63
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	4	1
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22	26	22
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30	37	30
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	0	1
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	0	1
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
PECO Energy Co [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			14
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19		19
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7		7
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current regulatory assets		267	214	267
Noncurrent regulatory assets		514	510	514
Regulatory Assets		781	724	781
Business Combination, Integration Related Costs		5	2
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Baltimore Gas and Electric Company [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 79	78	79
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		10 years
Noncurrent regulatory assets		$ 196	128	196
Regulatory Assets		196	128	196
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Baltimore Gas and Electric Company [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8	9	8
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Baltimore Gas and Electric Company [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9	12	9
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19	16	19
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	1	1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0	0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		40	15	40
Business Combination, Integration Related Costs			4
Baltimore Gas and Electric Company [Member] | Under Recovered Electric Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		28	10	28
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3	2
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		20	30	20
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		87	160	87
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		278	248	278
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6	8	6
Baltimore Gas and Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		3
Baltimore Gas and Electric Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30	7	30
Baltimore Gas and Electric Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		3
Over Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Over Recovered electric Supply Costs		29	3
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 19	$ 28	$ 19