Commitments and Contingencies - Other Purchase Obligations (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	$ 917
2014	103
2015	324
2016	180
2017	151
2018	36
Thereafter	123
Exelon Generation Co L L C [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	2,008
2014	104
2015	578
2016	450
2017	303
2018	129
Thereafter	444
Exelon Generation Co L L C [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	493	[1],[2]
2014	80	[1],[2]
2015	182	[1],[2]
2016	57	[1],[2]
2017	43	[1],[2]
2018	30	[1],[2]
Thereafter	101	[1],[2]
Commonwealth Edison Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	92	[3]
2014	13	[3]
2015	38	[3]
2016	16	[3]
2017	5	[3]
2018	5	[3]
Thereafter	15	[3]
PECO Energy Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	29	[3]
2014	7	[3]
2015	11	[3]
2016	2	[3]
2017	1	[3]
2018	1	[3]
Thereafter	7	[3]
Baltimore Gas and Electric Company [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	302	[3]
2014	2	[3]
2015	93	[3]
2016	105	[3]
2017	102	[3]
2018	0	[3]
Thereafter	$ 0	[3]

[1] Purchase obligations do not include commitments related to construction contracts. See Construction Commitments section below for additional information.

[2] Purchase obligations include commitments related to assets-held-for-sale. See Note 4 - Mergers, Acquisitions and Dispositions for additional information.

[3] Purchase obligations include commitments related to smart meter installation. See Note 5 — Regulatory Matters for additional information.