Commitments and Contingencies - Other Purchase Obligations (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	$ 840
2014	258
2015	279
2016	152
2017	38
2018	30
Thereafter	83
Exelon Generation Co L L C [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	2,028
2014	454
2015	560
2016	387
2017	177
2018	138
Thereafter	312
Exelon Generation Co L L C [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	364	[1],[2]
2014	123	[1],[2]
2015	81	[1],[2]
2016	43	[1],[2]
2017	31	[1],[2]
2018	23	[1],[2]
Thereafter	63	[1],[2]
Commonwealth Edison Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	152	[3]
2014	53	[3]
2015	82	[3]
2016	2	[3]
2017	2	[3]
2018	2	[3]
Thereafter	11	[3]
PECO Energy Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	11	[3]
2014	5	[3]
2015	6	[3]
2016	0	[3]
2017	0	[3]
2018	0	[3]
Thereafter	0	[3]
Baltimore Gas and Electric Company [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	313	[3]
2014	77	[3]
2015	110	[3]
2016	107	[3]
2017	5	[3]
2018	5	[3]
Thereafter	$ 9	[3]

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

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmVmN2Y3ZjVlMDU4YzQwMGVhOTA4ZWJkNWMzOGFmYjNhfFRleHRTZWxlY3Rpb246MUZCNTc2MzY0RjBDMkQwMTJFNTEwOTNBRjYwNTQ5M0IM}

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