Commitments and Contingencies (Other Commitments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 tons
Other Commitments:
Contractual obligation, 2014	$ 517
Contractual obligation, 2015	294
Contractual obligation, 2016	285
Contractual obligation, 2017	227
Contractual obligation, 2018	217
number of employees	1,047
Collective Bargaining Agreement Percentage Of Employee Participants	42.00%
Gas transportation agreements
Other Commitments:
Purchase commitments, aggregate	32
Agreement to re-sell, aggregate amount	39
Midwest Generation LLC [Member]
Other Commitments:
number of employees	586
Collective Bargaining Agreement Percentage Of Employee Participants	75.00%
Midwest Generation LLC [Member] | Coal Supply Agreements [Member]
Other Commitments:
Purchase obligation, 2014	194
Purchase obligation, 2015	0
Purchase obligation, 2016	0
Purchase obligation, 2017	0
Purchase obligation, 2018	0
Long-term Purchase Commitment, Minimum Quantity Required	9,800,000
Midwest Generation LLC [Member] | Coal transportation agreements
Other Commitments:
Minimum commitments, 2014	259	[1]
Minimum commitments, 2015	257	[1]
Minimum commitments, 2016	257	[1]
Minimum commitments, 2017	213	[1]
Minimum commitments, 2018	212	[1]
Purchase commitments, aggregate	1,800
Midwest Generation LLC [Member] | Capital expenditures
Other Commitments:
Minimum commitments, 2014	9
Minimum commitments, 2015	0
Minimum commitments, 2016	0
Minimum commitments, 2017	0
Minimum commitments, 2018	0
Midwest Generation LLC [Member] | Other contractual obligations
Other Commitments:
Minimum commitments, 2014	15
Minimum commitments, 2015	0
Minimum commitments, 2016	0
Minimum commitments, 2017	0
Minimum commitments, 2018	0
Other EME Subsidiaries | Other contractual obligations
Other Commitments:
Minimum commitments, 2014	33
Minimum commitments, 2015	30
Minimum commitments, 2016	20
Minimum commitments, 2017	7
Minimum commitments, 2018	2
Purchase commitments, aggregate	107
Other EME Subsidiaries | Gas transportation agreements
Other Commitments:
Minimum commitments, 2014	7
Minimum commitments, 2015	7
Minimum commitments, 2016	8
Minimum commitments, 2017	7
Minimum commitments, 2018	$ 3

[1] Years 2014 through 2018 reflect a reduction in minimum volumes for the voluntarily cessation of coal-fired operations at the Fisk and Crawford Stations.