Compensation and Benefit Plans (Benefit Payments) (Details) (USD $) In Millions, unless otherwise specified		12 Months Ended		12 Months Ended
	Mar. 01, 2012	Dec. 31, 2011 Pension Plans	Dec. 31, 2012 Pension Plans	Dec. 31, 2012 Pension Plans Midwest Generation LLC	Dec. 31, 2011 Pension Plans Midwest Generation LLC	Dec. 31, 2012 Pension Plans Other EME Subsidiaries		Dec. 31, 2011 Pension Plans Other EME Subsidiaries		Dec. 31, 2012 Postretirement Benefits Other Than Pensions	Dec. 31, 2012 Postretirement Benefits Other Than Pensions Midwest Generation LLC	Dec. 31, 2012 Postretirement Benefits Other Than Pensions Other EME Subsidiaries
Benefit payments expected to be paid, net:
2013, estimated future benefit payments			$ 12	$ 8		$ 4	[1]			$ 2	$ 1	$ 1	[1]
2014, estimated future benefit payments			14	9		5	[1]			2	1	1	[1]
2015, estimated future benefit payments			15	10		5	[1]			3	2	1	[1]
2016, estimated future benefit payments			16	12		4	[1]			3	2	1	[1]
2017, estimated future benefit payments			17	13		4	[1]			4	2	2	[1]
2018-2022, estimated future benefit payments			89	68		21	[1]			27	16	11	[1]
After tax value of post retirement benefits to be assumed by Edison International	25
Curtailment adjustment		$ 0		$ 0	$ 0	$ (9)	[2]	$ 0	[2]

[1] Excludes Homer City.

[2] Includes Homer City.