Commitments and Contingencies - Schedule of Energy Supply Procurement, Curtailment Services, REC and AEC Purchase Commitments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Commonwealth Edison Co [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Term of contract	20 years
Commonwealth Edison Co [Member] | DSP Program Electric Procurement Contracts [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	620	[1]
2015	329	[1]
2016	151	[1]
2017	140	[1]
2018	0	[1]
2019	0	[1]
Thereafter	0	[1]
Commonwealth Edison Co [Member] | Renewable Energy Including Renewable Energy Credits [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	1,517	[2]
2015	75	[2]
2016	76	[2]
2017	77	[2]
2018	78	[2]
2019	84	[2]
Thereafter	1,127	[2]
PECO Energy Co [Member] | DSP Program Electric Procurement Contracts [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	609	[2]
2015	527	[3]
2016	82	[3]
2017	0	[3]
2018	0	[3]
2019	0	[3]
Thereafter	0	[3]
PECO Energy Co [Member] | Alternative Energy Credits [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	13	[4]
2015	2	[4]
2016	2	[4]
2017	2	[4]
2018	2	[4]
2019	2	[4]
Thereafter	3	[4]
Baltimore Gas and Electric Company [Member] | DSP Program Electric Procurement Contracts [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	1,315	[5]
2015	779	[5]
2016	448	[5]
2017	88	[5]
2018	0	[5]
2019	0	[5]
Thereafter	0	[5]
Baltimore Gas and Electric Company [Member] | Curtailment Services [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	115	[6]
2015	40	[6]
2016	34	[6]
2017	29	[6]
2018	12	[6]
2019	0	[6]
Thereafter	0	[6]

[1] ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up. As of December 31, 2014, ComEd has completed the ICC-approved procurement process for a portion of its energy requirements through the periods ending May 31, 2015, 2016 and 2017.

[2] Primarily related to ComEd 20-year contracts for renewable energy and RECs that began in June 2012. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. The commitments represent the maximum settlements with suppliers for renewable energy and RECs under the existing contract terms.

[3] PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2015 and 2016. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Programs. See Note 3 — Regulatory Matters for additional information.

[4] PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 3 — Regulatory Matters for additional information.

[5] BGE entered into various contracts for the procurement of electricity beginning 2015 through 2017. The cost of power under these contracts is recoverable under MDPSC approved fuel clauses. See Note 3 — Regulatory Matters for additional information.

[6] BGE has entered into various contracts with curtailment services providers related to transactions in PJM’s capacity market. See Note 3 — Regulatory Matters for additional information.