Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended								3 Months Ended		9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012	Sep. 30, 2013 IRS Examination	Sep. 30, 2013 Midwest Generation LLC	Dec. 31, 2012 Midwest Generation LLC	Sep. 30, 2013 Edison International	Sep. 30, 2012 Edison International	Sep. 30, 2013 Edison International	Sep. 30, 2012 Edison International	Dec. 31, 2012 Hypothetical Tax Return Midwest Generation LLC
Income Tax Disclosures:
State tax expense (benefit)									$ (1)	$ 2	$ 0	$ 7
NonCash Contribution From Parent	32	[1]	0	[2]
Net tax allocation payments received under tax allocation agreement	7
Cash Contribution From Parent	6	[1]
TotalContributionsFromParent	38
Valuation allowance	742				444		776	533
Valuation Allowance, Amount	167
Estimated potential future federal tax payment as of the balance sheet date, including interest and penalties, based on a proposed adjustment						205
Interest From Income Tax Examination						57
Penalties From Income Tax Examination						42
Noncash Distribution of Tax Benefits To Parent													$ 106

[1] During 2013, EME received contributions from EIX related to the tax-allocation agreements. For further information, see Note 7—Income Taxes—EME—Effective Tax Rate.

[2] During 2013, the non-cash contribution from EIX relates to the tax-allocation agreements. For further information, see Note 7—Income Taxes—EME—Effective Tax Rate.